A novel IPv6 address configuration for a 6LoWPAN-based WBAN

Journal of Network and Computer Applications ∎ (∎∎∎∎) ∎∎∎–∎∎∎

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A novel IPv6 address configuration for a 6LoWPAN-based WBAN Xiaonan Wang n, Hongbin Chen, Deguang Le Changshu Institute of Technology, Changshu, Jiangsu 215500, China

art ic l e i nf o

a b s t r a c t

Article history: Received 5 December 2014 Received in revised form 26 August 2015 Accepted 2 October 2015

Wireless body area networks are used to collect the physical parameters of the human body for monitoring. Before a wireless body area network can perform the effective and proper communication, each node in the network must be configured with a unique address. The address configuration solutions for wireless networks are usually classified into two categories: stateless solutions and stateful solutions. In the stateless approaches, duplicate address detection is employed to ensure the address uniqueness and inevitably this flooding increases the addressing cost and delay. By contrast, the stateful solutions can guarantee the address uniqueness without duplicate address detection. However, a node has to acquire an address from a remote server multi-hop away, so the address configuration cost and delay are relatively high. Moreover, the stateful solutions must store the address allocation information and perform the address reclamation. In order to reduce the addressing cost and delay, this paper proposes an address configuration scheme for a 6LoWPAN-based wireless body area network. In this scheme, the address uniqueness can be guaranteed without duplicate address detection, so address configuration cost and delay are reduced. Moreover, the released addresses can be automatically reclaimed without any extra operations, so there is always an abundant address space available for allocation. The performance of this scheme is evaluated, and the data results show that this scheme reduces the address configuration delay and cost. & 2015 Elsevier Ltd. All rights reserved.

Keywords: Wireless body area network 6LoWPAN IPv6 address Address configuration Address reclamation

1. Introduction Small and intelligent devices attached to the body form a wireless body area network (WBAN), and typically these devices might be sensor nodes (Latré et al., 2011). The sensors are used to collect the physical parameters of the human body for monitoring, including the heart rate, blood level, body temperature or electrocardiogram (ECG). Then, the sensor nodes send the collected physical data to the medical staff so that these data can be monitored and managed in real time. The Internet Protocol version 6 (IPv6) is the latest IP version which has large address spaces, and the Low-power Wireless Personal Area Network (LoWPAN) can support the low-cost communications. The Internet Engineering Task Force (IETF) has proposed the IPv6 over LoWPAN (6LoWPAN) (Kushalnagar et al., 2007) to achieve the all-IP communication between the LoWPAN and the IPv6 internet. As a typical example of LoWPAN, a WBAN must perform the communication with the Internet in order to send the collected data to medical staff. Before sensor nodes in a WBAN perform the effective and proper communication, they must be configured with a unique address (Movassaghi et al., 2014; Al-Surmi et al., 2012). In general, n

the address configuration scheme for a WBAN should achieve the following objectives (Movassaghi et al., 2014): 1) Uniqueness. The address configuration scheme must guarantee that each node's address is unique in the network because duplicate addresses can cause improper communications. 2) Low cost. A WBAN has limited resources, such as energy, computing capability, etc (Latré et al., 2011; Cavallari et al., 2014), so the address configuration cost should be low in order to reduce resource consumption. 3) Low delay. In a WBAN, sensor nodes are attached to the human body, so one main characteristic of a WBAN is mobility. Hence, a sensor node should acquire an address before it moves out of its upstream node's communication range. Moreover, data collected by a WBAN are generally medical parameters, so the address configuration delay should be low in order to ensure that these data can be sent to medical staff in real time. 4) Address reclamation. In order to ensure there is always an abundant address space available for allocation, released addresses should be reclaimed for reuse. Taking these objectives into account, this paper proposes an address configuration scheme for a 6LoWPAN-based WBAN, and it has the following contributions:

Corresponding author.

http://dx.doi.org/10.1016/j.jnca.2015.10.013 1084-8045/& 2015 Elsevier Ltd. All rights reserved.

Please cite this article as: Wang X, et al. A novel IPv6 address configuration for a 6LoWPAN-based WBAN. Journal of Network and Computer Applications (2015), http://dx.doi.org/10.1016/j.jnca.2015.10.013i

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1) The network architecture is proposed. This network model is made up of a backbone and multiple WBANs. The nodes in a WBAN communicate with the Internet via the backbone. A WBAN is made up of an active mobile full-function device (FFD) and a few reduced-function devices (RFDs). In order to differentiate a mobile FFD from an RFD, the node type is included in the address structure. In this way, the uniqueness of a mobile FFD's address in a WBAN can be guaranteed without performing duplicate address detection (DAD) or storing address allocation information. 2) In a WBAN, physical parameters each sensor node collects are usually different, so this scheme makes use of the physical parameters to achieve the address configuration in order to reduce the address configuration cost and delay. 3) The address reclamation algorithm is proposed in order to ensure that there is an abundant address space available for allocation. Since the address configuration for an RFD is achieved without storing the address allocation information, the address space occupied by an RFD can be automatically reclaimed without any operations. In this way, the average address reclamation cost and delay are reduced.

configuration for different clusters can be fulfilled in parallel, so this scheme has better performance than MANETconf. Hussain et al. (2011) propose a location-based address configuration scheme. In this scheme, a node employs the global positioning system to obtain the location information which is used to construct an address. Then, distributed DAD servers perform DAD for this address to ensure the address uniqueness. However, it is hard for a mobile node to work as a DAD server, and it is also unrealistic to equip each node with the global positioning system. Kim et al. (2007) propose an optimistic DAD. In this scheme, a node with reserved addresses is referred as a type-1 node, a node with no reserved addresses is defined as a type-2 node, and a new node is a type-3 node. A type-3 node first requests an address from a neighbor node. If this neighbor is a type-1 node, it directly assigns an address to the type-3 node. Otherwise, this neighbor borrows an address from a type-1 node and assigns the address to the type-3 node. Then, the type-3 node performs DAD to ensure the address uniqueness. If the type-3 node acquires two unique addresses, then it changes into a type-1 node. Otherwise, it changes into a type-2 node. 2.2. Stateful address configuration

The remainder of this paper is organized as follows. In Section 2, the related work on the address configuration schemes is discussed. The address configuration algorithm and address reclamation algorithm are presented respectively in Sections 3 and 4. The performance of this scheme is analyzed and evaluated in Sections 5 and 6. This paper concludes with a summary in Section 7.

2. Related work At present, two standardized protocols including the stateless protocol (Thomson et al., 2007) and stateful protocol (Droms et al., 2003) are used to achieve the IPv6 address configuration. The stateless protocol performs DAD to ensure the uniqueness of an address, so the address configuration cost and delay are relatively high. The stateful protocol is based on the client/server mode. That is, a node acquires a unique address from a remote dynamic host configuration protocol (DHCP) server. This model has two deficiencies: (1) The distance between a node and a remote server is usually multi-hop away, so the route must be established between them before the node requests an address from the remote server. As a result, the address configuration cost and delay are increased. (2) After a mobile node requests an address from a remote server, its position may change. This may result in the route reestablishment, and the address configuration performance is further degraded. Consequently, these two standardized protocols are unsuitable for a WBAN. At present, some address configuration solutions are proposed for wireless networks, and they are classified into two categories: stateless solutions and stateful solutions (Ancillotti et al., 2009). 2.1. Stateless address configuration In the stateless solutions, each node configures itself with an IP address, and then performs DAD to verify the address uniqueness. Nesargi and Prakash (2002) propose an address configuration scheme for a mobile ad hoc network-MANETconf. In MANETconf, a new node first requests an address from an initiator, and then broadcasts this address in the network to ensure the uniqueness of this address. Obviously, DAD increases the address configuration cost and delay. In (Wang and Qian, 2012), the address configuration based on clusters is proposed. In this scheme, a cluster member performs DAD within a cluster and the address

In the stateful schemes, the address allocation information is maintained and based on this information the address configuration is performed, so the address uniqueness can be guaranteed without DAD. In Ghosh and Datta (2011), a new node requests an address from the neighbor proxy node with the minimum address. If the proxy node has the address resources, then it directly assigns an address to the new node. Otherwise, the proxy node requests the address resources from its ancestor nodes. In the latter case, the address configuration performance is degraded. In addition, the first new node sets its address to 0. If more than one new node joins a network at the same time, then the address conflict might happen. Talipov et al. (2011) propose a proxy-based address configuration scheme. In this scheme, the random ID and time stamp are used to identify a new node. If two nodes with the same ID and time stamp request an address from a proxy node, then the proxy node is unable to distinguish between these two nodes. As a result, the address configuration cannot be performed correctly. Moreover, the neighbor solicitation and neighbor advertisement are used to perform the communication between a new node and a proxy node while REQ and REP are employed to fulfill the communication between a proxy node and a gateway node. Therefore, a proxy node has to store the mapping between these two kinds of messages, so the address configuration performance is potentially degraded. Ozturk and Nagarnaik (2011) propose a dynamic address allocation protocol where the IP address structure consists of the network ID, node ID and port number. The network is organized into a tree structure where an intermediate node has two addresses and a leaf node has one address. A new node acquires an IP address through joining a tree structure and the address uniqueness is ensured without DAD. Al-Mistarihi et al. (2011) propose a tree-based dynamic address auto-configuration protocol-T-DAAP. T-DAAP defines three kinds of nodes: a normal node which acts as a relay, a leader node which is responsible for address configuration, and a root node which stores the information on all leader nodes and is responsible for address reclamation and network merging. If the root node fails or moves out of the network, then the network cannot work normally. In Gammar et al. (2010), a node broadcasts an address recovery message to reclaim the address resources. If a node's address is within the reclaimed address space, then it returns a response message to show its active status. Then, this node also broadcasts

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an address recovery message. In this scheme during one address recovery process almost each proxy nodes broadcasts a message, so the address reclamation cost and delay are relatively high.

From the above analysis, it can be seen that the stateless schemes must perform DAD to ensure the address uniqueness. As a result, the address configuration cost and delay are relatively high. Although the stateful solutions can ensure the address uniqueness without DAD, they must store the address configuration information and perform the address reclamation. Moreover, if a node acquires an address from a remote server multi-hop away, then the address configuration cost and delay are relatively high. In order to overcome the disadvantages in stateless and stateful solutions, this paper proposes the following innovations:

3. IPv6 address configuration 3.1. Architecture The link protocol in 6LoWPAN is IEEE 802.15.4 (LAN/MAN Standards Committee, 2011) which classifies nodes into FFDs with a routing function and RFDs without a routing function. This scheme divides FFDs into fixed FFDs and mobile FFDs. Fixed FFDs construct a backbone network which is connected to the IPv6 Internet via an access router (AR). A WBAN is made up of mobile FFDs and RFDs. Among them, only one mobile FFD is active, and other mobile FFDs are in the dormant state. A mobile FFD achieves the communication with the Internet through the backbone, and an RFD performs the communication with other nodes via a mobile FFD, as shown in Fig. 1. In a WBAN, each node carries n (n Z1) sensors which are used to sense and collect physical parameters. 3.2. IPv6 address structure Based on the architecture, this scheme proposes the following IPv6 address structure, as shown in Table 1. As shown in Table 1, an IPv6 address consists of 7 parts. The first part is the global network prefix. The global network prefixes of all fixed FFDs in the backbone are the same, and the value is equal to the one of the AR which the backbone is connected to. The second part is FFFD ID which uniquely identifies a fixed FFD. The third part is MFFD ID which uniquely identifies a mobile FFD. The fourth part is node type. If the node type of a node is equal to 0, then it means that this node is a mobile FFD. Otherwise, this node is an RFD. The fifth part is number of sensors, and it indicates the number of the sensors a node carries. The sixth part is set of sensor ID, and it is the set of the sensor IDs of the sensors carried by a node. The seventh part is inner ID which is used to distinguish the RFDs with the same number of sensors and the same set of sensor

Wired connection Wireless connection

Access router Mobile FFD Fixed FFD RFD User

2.3. Our solution

1) The node type is included in the address structure in order to differentiate an FFD from an RFD in a WBAN. In this way, the address uniqueness in a WBAN can be guaranteed without performing DAD or storing address allocation information. 2) The physical parameters each sensor node collects are usually different, so they are used to achieve the address configuration in order to reduce the address configuration cost and delay. 3) The address configuration can be achieved without storing the address allocation information, so the address space can be automatically reclaimed without any operations. In this way, the average address reclamation cost and delay are reduced.

3

IPv6 Internet

Backbone Body sensor network Fig. 1. Architecture. Table 1 IPv6 address structure. Bits: 64

i

j

1

m

Global network prefix

FFFD ID MFFD ID Node type Number of sensors Link address

k

60-i-j-k-m

Set of sensor ID

Inner ID

ID in a WBAN. A link address is made up of the latter six parts, namely from the second part to the seventh part. The FFFD ID, MFFD ID, node type, number of sensors and set of sensor ID of an AR are zero, and the inner ID is 1. The MFFD ID, node type, number of sensors, set of sensor ID and inner ID of a fixed FFD are all zero, and the FFFD ID is not zero. In this scheme, the fixed FFDs are distributed around the backbone and the number of the mobile FFDs is proportional to the number of WBANs, so i is determined by the backbone area, j is by the number of users, m is by the number of the sensors carried by a node, k is by m and the length l of a sensor ID, and k, m and l satisfy the inequation: k Zm
l. In a WBAN, the number of the RFDs with the same number of sensors and the same set of sensor ID are usually small, so the length of the inner ID can be small. Taking the generality and readability into account, we set i and j to 16. The maximum number of the sensors carried by a node is 6, so m is set to 3. A kind of sensor can only sense one type of physical parameter and is defined by a sensor ID. The types of the sensors are at most 15, so l is 4-bit long and k is set to 24. In the set of sensor ID, the sensor IDs are sorted in the ascending order. For example, the first 4 bits are the sensor ID 0001 of the sensor which senses the heart rate, and the next 4 bits are the sensor ID 0010 of the sensor which senses the blood level, and so on. 3.3. Address initialization In this scheme, an AR's address is pre-set, a fixed FFD acquires an address from an AR or a configured fixed FFD, a mobile FFD obtains an address from a configured fixed FFD or mobile FFD, and an RFD gets the address prefix from the mobile FFD in the same WBAN and then configures itself with an address. An AR maintains an FFFD ID allocation table which records the assigned FFFD ID space, and an entry consists of two fields: the upper limit and lower limit of the assigned FFFD ID space. An FFD maintains an MFFD ID allocation table which records the assigned

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MFFD ID space, and an entry consists of three fields: the upper limit and lower limit of the assigned MFFD ID space, and the life time. This scheme expands the beacon frames to achieve the address configuration. In a beacon frame, the first 4 bits define the type and payload of a beacon frame, as shown in Table 2. After an AR, a fixed FFD, a mobile FFD or an RFD acquires an address, it broadcasts a type-0 beacon frame within onehop scope. 3.3.1. Address initialization for fixed FFD After a fixed FFD X starts, it listens to the type-0 beacon frames from an AR or a configured fixed FFD. Then, X selects the AR or fixed FFD with the maximum length of the unassigned FFFD ID space and constructs a temporary address where the global network prefix is set to the one of the selected AR or fixed FFD and the FFFD ID is set to the hardware ID, for example, the media access control (MAC) address. X acquires an address from the neighbor AR AR1 according to the following process: 1) X sends AR1 a type-1 beacon frame where the source address is its temporary link address. 2) After AR1 receives this type-1 beacon frame, it selects the unassigned FFFD ID space [L, U] (L and U are positive integers, and L is less than U), and returns X a type-2 beacon frame where the payload is the lower limit L and the upper limit U of the FFFD ID space. Then, AR1 adds into its FFFD ID allocation table an entry where the upper limit is U and the lower limit is L. 3) After X receives the type-2 beacon frame, it sets the FFFD ID to L and the FFFD ID space to [Lþ 1, U]. In this way, X acquires an address where the global routing prefix is the same as the one in the temporary address. 4) The address configuration is complete, as shown in Fig. 2 (a) and (b). A fixed FFD Y acquires an address from the neighbor fixed FFD X with the FFFD ID space [L1, U] according to the following process: 1) Y sends X a type-1 beacon frame where the source address is its temporary link address. 2) After X receives this type-1 beacon frame, it returns Y a type-2 beacon frame where the payload is the lower limit ⌈(L1 þU)/2⌉ Table 2 Expanded beacon frames.

Fig. 2. Address initialization for fixed FFD.

and the upper limit U of the FFFD ID space. Then, X updates its FFFD ID space with [L1, ⌈(L1 þU)/2⌉  1]. 3) After Y receives the type-2 beacon frame, it sets the FFFD ID to ⌈ (L1 þU)/2⌉ and the FFFD ID space to [⌈(L1 þ U)/2⌉þ 1, U]. In this way, Y acquires an address where the global routing prefix is the same as the one in the temporary address. 4) The address configuration is complete, as shown in Fig. 2(a).

Type(H) Payload 0

1 2 3 4 5 6 7 8 9 A

In a beacon frame broadcasted by an AR, the payload includes the global network prefix and the length of the unassigned FFFD ID space. In a beacon frame broadcasted by a fixed FFD, the payload includes the global network prefix, the length of the unassigned FFFD ID space, and the length of the unassigned MFFD ID space. In a beacon frame broadcasted by a mobile FFD, the payload includes the global network prefix, and the upper limit and lower limit of its MFFD ID space. Empty. The assigned FFFD ID space. Empty. The assigned MFFD ID space. Empty. The occupied FFFD ID space. The occupied MFFD ID space. Empty. The old address and the global network prefix of the new address. The address of a failed mobile FFD and the upper limit and lower limit of the MFFD ID space.

In Fig. 2(a), at the time T1, X requests an FFFD ID from AR1. AR1 assigns the FFFD ID space (Latré et al., 2011; Ancillotti et al., 2009) to X, and X sets the FFFD ID to 1 and the FFFD ID space to (Kushalnagar et al., 2007; Ancillotti et al., 2009). At the time T2, Y requests an FFFD ID from X. X assigns the FFFD ID space (Cavallari et al., 2014; Ancillotti et al., 2009) to Y and updates its FFFD ID space with (Kushalnagar et al., 2007; Al-Surmi et al., 2012). Y sets its FFFD ID to 5 and the FFFD ID space to (Thomson et al., 2007; Ancillotti et al., 2009).

3.3.2. Address initialization for mobile FFD After a mobile FFD Z starts, it listens to the type-0 beacon frames from a configured fixed FFD or mobile FFD. Then, Z selects the fixed FFD or mobile FFD with the maximum length of the unassigned MFFD ID space and constructs a temporary address where the global network prefix and FFFD ID are set to the ones of

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the selected fixed FFD or mobile FFD and the MFFD ID is set to the hardware ID, for example, the MAC address. Z acquires an address from the neighbor fixed FFD Y according to the following process: 1) Z sends Y a type-3 beacon frame where the source address is its temporary link address. 2) After Y receives this type-3 beacon frame, it selects the unassigned MFFD ID space [L, U], and returns Z a type-4 beacon frame where the payload is the lower limit L and the upper limit U of the MFFD ID space. Then, Y adds into its MFFD ID allocation table an entry where the upper limit is U and the lower limit is L. 3) After Z receives the type-4 beacon frame, it sets the MFFD ID to L and the MFFD ID space to [Lþ1, U]. In this way, Z acquires an address where the global routing prefix and FFFD ID are the same as the ones in the temporary address and the node type is 0. A mobile FFD M acquires an address from the neighbor mobile FFD Z with the FFFD ID space [L1, U] according to the following process: 1) M sends Z a type-3 beacon frame where the source address is its temporary link address. 2) After Z receives this type-3 beacon frame, it returns M a type-4 beacon frame where the payload is the lower limit ⌈(L1 þ U)/2⌉ and the upper limit U of the MFFD ID space. Then, Z updates its MFFD ID space with [L1, ⌈(L1 þU)/2⌉-1]. 3) After M receives the type-4 beacon frame, it sets the MFFD ID to ⌈(L1 þU)/2⌉ and the MFFD ID space to [⌈(L1 þU)/2⌉þ1, U]. In this way, M acquires an address where the global routing prefix and FFFD ID are the same as the ones in the temporary address and the node type is 0. After Z or M performs the above process, it sets the number of sensors to the number of the sensors carried by itself, and the set of sensor ID to the collection of the sensor IDs of these sensors. At this stage, the address configuration is complete, as shown in Fig. 3. Then, Z or M broadcasts a type-0 become frame. After a mobile FFD receives the first type-0 beacon frame from a configured mobile FFD in the same WBAN, it enters the dormant state. In Fig. 3, at the time T1, Z requests an MFFD ID from Y. Y assigns the MFFD ID space (Latré et al., 2011; Al-Mistarihi et al., 2011) to Z, and Z sets the MFFD ID to 1 and the MFFD ID space to (Kushalnagar et al., 2007; Al-Mistarihi et al., 2011). At the time T2, M requests an MFFD ID from Z. Z assigns the MFFD ID space (Nesargi and Prakash, 2002; Al-Mistarihi et al., 2011) to M and updates its FFFD ID space with (Kushalnagar et al., 2007; Ancillotti et al., 2009). M sets its FFFD Access router Mobile FFD Fixed FFD RFD User

Wired connection Wireless connection IPv6 Internet

Y 3F99:1:2FEB:1:5::/80 MFFD ID table at T1: Lower limit Upper limit Life time 1 16 1000 Z 3F99:1:2FEB:1:5:1:2120::/96 M At T1 3F99:1:2FEB:1:5:9:1100::/96 MFFD ID space: [2,16] At T2 [1,16] At T2 MFFD ID space: [10,16] MFFD ID space: [2,8] [9,16] R4 R1 3F99:1:2FEB:1:5:1:9300:1/96 3F99:1:2FEB:1:5:9:9200::/96 R5 R2 3F99:1:2FEB:1:5:1:9300:2/96 3F99:1:2FEB:1:5:9:9300::/96 R3 3F99:1:2FEB:1:5:1:9300::/96

Fig. 3. Address initialization for mobile FFD and RFD.

5

ID to 9 and the MFFD ID space to (Wang and Qian, 2012; Al-Mistarihi et al., 2011). Z carries two sensors whose sensor IDs are respectively 0001 and 0010, so it sets the number of sensors to 2, the first 4 bits in the set of sensor ID to 0001, the next 4 bits to 0010 and the remaining bits to 0. M carries one sensor whose sensor ID is 0001, so it sets the number of sensors to 1, the first 4 bits in the set of sensor ID to 0001 and the remaining bits to 0. 3.3.3. Address initialization for RFD In general, an RFD carries different types of sensors, so it uses the sensor IDs to achieve the address configuration in order to reduce address conflict. After an RFD starts, it listens to the type-0 beacon frames from a configured mobile FFD. Then, the RFD selects the configured mobile FFD with the strongest signal, and sets its global network prefix, FFFD ID and MFFD ID to the ones of the selected mobile FFD, the node type to 1, the number of sensors to the number of the sensors carried by itself, and the set of sensor ID to the collection of the sensor IDs of these sensors. In Fig. 3, the RFDs R1 and R2 acquire the global network prefix, FFFD ID and MFFD ID from the mobile FFD M. R1 carries a sensor whose sensor ID is 0010, so it sets the number of sensors to 1, the first 4 bits in the set of sensor ID to 0010 and the remaining bits to 0. R2 also carries one sensor whose sensor ID is 0011, so it sets the number of sensors to 1, the first 4 bits in the set of sensor ID to 0011 and the remaining bits to 0. Finally, R1 and R2 set their inner IDs to 0. In the extreme cases, if more than one RFD carries the same number of sensors and the same set of sensor ID, then the address conflict occurs. In this situation, the inner ID is used to distinguish between these RFDs. Since all the RFDs in a WBAN are neighbors, one RFD can receive the beacon frames from other RFDs in the same WBAN. When an RFD R3 obtains an IPv6 address where the inner ID is e, it broadcasts a type-0 beacon frame. After an RFD R4 in the same WBAN receives this beacon frame, it compares its link address with the source address of the received beacon frame. If R4 detects that in its link address the number of sensors and set of sensor ID are the same as the ones in R3's link address, then it performs e¼eþ1 and sets its inner ID to e. Then, R4 broadcasts a type-0 beacon frame. The process is repeated until all the RFDs in a WBAN all broadcast a type-0 beacon frame. In Fig. 3, R3, R4 and R5 have the same number of sensors and set of sensor ID, so they use the inner ID to ensure the address uniqueness. That is, R3's inner ID is 0, R4's inner ID is 1, and R5's inner ID is 2. In this way, R3, R4 and R5 acquire respectively a unique address. 3.4. Address configuration for new nodes 3.4.1. Address configuration for new fixed FFD After the address initialization is complete, a new fixed FFD joining the network acquires an address via the address initialization algorithm in Section 3.3.1. 3.4.2. Address configuration for new mobile FFD After the address initialization is complete, a new mobile FFD joining the network acquires an address via the address initialization algorithm in Section 3.3.2. 3.4.3. Address configuration for new RFD After the address initialization is complete, a new RFD joining the network listens to the type-0 beacon frames broadcasted by a configured mobile FFD. Then, the RFD selects the configured mobile FFD with the strongest signal, and sets its global network prefix, FFFD ID and MFFD ID to the ones of the selected mobile FFD, the node type to 1, the number of sensors to the number of

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the sensors carried by itself, the set of sensor ID to the collection of the sensor IDs of these sensors, and the inner ID to 0. Then, the new RFD listens to the beacon frames broadcasted by the RFDs in the same WBAN. After an RFD receives a beacon frame, it compares its link address with the source address of the received beacon frame. If the new RFD detects that in its link address the number of sensors and set of sensor ID are the same as the ones in the source address, then it stores the source address of the received beacon frame. The above process is repeated until the RFD receives the beacon frames from all the RFDs in the same WBAN and records the addresses with the same number of sensors and set of sensor ID. Finally, based on these recorded addresses the RFD selects a minimum unassigned inner ID as its inner ID. In this way, the uniqueness of the RFD's address is ensured.

AR1 3F99:1:2FEB:1::1/64 FFFD ID table at T1: Lower limit Upper limit 1 8 FFFD ID table at T2: Lower limit Upper limit 1 2 5 6 7 8 FFFD ID table at T3: Lower limit Upper limit 1 2 5 8

Access router Fixed FFD Wired connection Wireless connection

IPv6 Internet

X1 3F99:1:2FEB:1:3::/80

X 3F99:1:2FEB:1:1::/80 4. Address reclamation 4.1. Address reclamation for fixed FFD

FFFD ID space: [4,4]

FFFD ID space: [2,2]

Y 3F99:1:2FEB:1:5::/80 FFFD ID space: [6,6]

An AR regularly initiates the FFFD ID reclamation process to ensure that it has always enough FFFD ID space for allocation. The AR AR1 launches the following algorithm to reclaim the FFFD ID space:

Y1 3F99:1:2FEB:1:7::/80 FFFD ID space: [8,8]

1) AR1 empties the FFFD ID allocation table, and broadcasts a type5 beacon frame. 2) After a configured fixed FFD with the same global network prefix receives this type-5 frame, it returns AR1 a type-6 beacon frame where the payload is the upper limit U and lower limit L of its FFFD ID space, and then forwards this type-5 beacon frame to its neighbors. 3) After AR1 receives the type-6 beacon frame from the configured fixed FFD, it adds into the FFFD ID allocation table an entry where the upper limit is U and the lower limit is L. 4) Repeat step (2) and step (3) until all active configured fixed FFDs with the same global network prefix return a type-6 beacon frame to AR1. 5) AR1 compares any two entries E1 and E2 in its FFFD ID allocation table. In E1, the upper limit is U1 and the lower limit is L1. In E2, the upper limit is U2 and the lower limit is L2. If the following requirements are satisfied, then AR1 merges E1 with E2, as shown as follows:

 L1¼ U2 þ1 

AR1 updates the lower limit in E1 with L2, and then deletes E2. L2¼ U1 þ1 AR1 updates the lower limit in E2 with L1, and then deletes E1.

6) The FFFD ID reclamation process is complete, as shown in Fig. 4 (a) and (b). In the above algorithm, if a configured fixed FFD fails, then it cannot return a type-6 beacon frame. As a result, AR1 can retrieve the FFFD ID space occupied by this fixed FFD. In Fig. 4(a), at the time T1, in AR1's FFFD ID allocation table there is an entry where the lower limit is 1 and the upper limit is 8. At the time T2, AR1 launches the FFFD ID reclamation process. Since the fixed FFD X1 fails, AR1 only receives the type-6 beacon frames from the fixed FFD nodes X, Y and Y1 and accordingly it adds three entries into its FFFD ID allocation table. At the time T3, AR1 merges these entries, and reclaims the FFFD ID space (Movassaghi et al., 2014; Al-Surmi et al., 2012) occupied by X1.

Fig. 4. Address reclamation for fixed FFD.

4.2. Address reclamation for mobile FFD A configured mobile FFD regularly sends a type-7 beacon frame to the configured fixed FFD with the same global network prefix and FFFD ID, and the payload in this frame includes the upper limit U and the lower limit L of its MFFD ID space. After the fixed FFD receives the type-7 beacon frame from the mobile FFD, it performs the following operations: 1) The fixed FFD returns a type-8 beacon frame to the mobile FFD. 2) The fixed FFD checks the MFFD ID allocation table. If there is an entry E1 which satisfies one of the following requirements, then the fixed FFD performs the corresponding operations. In E1, the upper limit is U1 and the lower limit is L1.

 L1 oL and U1 4U The fixed FFD adds into its MFFD ID allocation table two entries E2 and E3. In E2, the upper limit is U, the lower limit is L, and

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the life time is set to the maximum value. In E3, the upper limit is U1, and the lower limit is Uþ1. Then, the fixed FFD updates the upper limit in E1 with L  1. L1 ¼L and U14 U The fixed FFD adds one entry E2 into its MFFD ID allocation table. In E2, the upper limit is U, the lower limit is L, and the life time is set to the maximum value. In E1, the lower limit is updated with Uþ1. L1 oL and U1 ¼ U The fixed FFD adds one entry E2 into its MFFD ID allocation table. In E2, the upper limit is U, the lower limit is L, and the life time is set to the maximum value. In E1, the upper limit is updated with L  1. L1 ¼L and U1¼ U The fixed FFD sets the life time in E1 to the maximum value.

3) The fixed FFD checks each entry in its MFFD ID allocation date. If the life time in one entry attenuates to zero, then the fixed FFD deletes this entry. In this way, the MFFD ID space can be reclaimed, as shown in Fig. 5. In the above algorithm, if a configured mobile FFD fails, then it cannot send a type-7 beacon frame. In this situation, after the life time in the corresponding entry attenuates to zero, this entry is removed and the MFFD ID space occupied by this mobile FFD can be retrieved. In Fig. 5, at the time T1, in the fixed FFD Y's MFFD ID allocation table there is an entry where the lower limit is 1, the upper limit is 16 and the life time is 500 ms. At the time T2 which is equal to T1 þ100 ms, Y receives a type-7 beacon frame from the mobile FFD Z1 with the upper limit 8 and lower limit 5, so it sets the life time in the corresponding entry to the maximum value 1000 ms. At the time T3 which is equal to T2 þ100 ms, Y receives a type-7 beacon frame from the mobile FFD M1 with the upper limit 16 and lower limit 13, so it sets the life time in the corresponding entry to the maximum value 1000 ms. At the time T4 which is equal to T3 þ100 ms, Y receives a type-7 beacon frame from the mobile FFD Z with the upper limit 4 and lower limit 1, so it sets the life time in the corresponding entry to the maximum value 1000 ms. Since the mobile FFD M fails, it cannot send a type-7 beacon frame. At the time T5 which is equal to T4þ 200 ms, the life time in the corresponding entry attenuates to zero, so Y removes this entry from its Y 3F99:1:2FEB:1:5::/80 MFFD ID table at T1: Lower limit Upper limit Life time 1 16 500 MFFD ID table at T2 (T1+100): Lower limit Upper limit Life time 1 4 400 5 8 1000 9 16 400 MFFD ID table at T3(T2+100): Lower limit Upper limit Life time 1 4 300 5 8 900 9 12 300 13 16 1000 MFFD ID table at T4(T3+100): Lower limit Upper limit Life time 1 4 1000 5 8 800 9 12 200 13 16 900 MFFD ID table at T5(T4+200): Lower limit Upper limit Life time 1 4 800 5 8 600 13 16 700

7

MFFD ID allocation table and the MFFD ID space (Nesargi and Prakash, 2002; Kim et al., 2007) occupied by M is reclaimed. If a mobile FFD does not receive a type-8 beacon frame returned by the fixed FFD, then it considers that this fixed FFD fails. In this situation, the mobile FFD reacquires an address and then broadcasts a type-9 beacon frame where the payload is its old address and the global network prefix of its new address. After an RFD in the same WBAN receives this type-9 beacon frame, according to the old address in the frame it can determine that this frame comes from the mobile FFD in the same WBAN. Therefore, the RFD updates its global network prefix with the one in the beacon frame, and FFFD ID and MFFD ID with the ones of the source address of the received beacon frame. In this scheme, a mobile FFD is equipped with a hardwaretrigger device which can receive signals from other nodes to awaken this mobile FFD from a dormant state (Wang et al., 2012). If an RFD does not receive a frame from the mobile FFD in the same WBAN within the specified time, then it considers that this mobile FFD fails. In this case, the RFD activates another mobile FFD and then broadcasts a type-A beacon frame where the payload is the address of the failed mobile FFD and the upper limit and lower limit of the MFFD ID space. After the triggered mobile FFD receives this type-A beacon frame, it sets its address and MFFD ID space to the ones in the frame. In this way, even if the mobile FFD fails, the corresponding WBAN can still work in the normal state.

4.3. Address reclamation for RFD This scheme uses the sensor IDs to achieve the address configuration for an RFD, so it does not need to perform the address reclamation.

5. Analysis We analyze the performance of this scheme, including the address configuration cost and delay, and the address reclamation cost and delay. The cost is measured by the total number of the beacon frames used for the address configuration or reclamation.

Mobile FFD Fixed FFD User

M 3F99:1:2FEB:1:5:9:1100::/96 MFFD ID space: [10,12] Z 3F99:1:2FEB:1:5:1:2120::/96 MFFD ID space: [2,4] Z1 3F99:1:2FEB:1:5:5:2120::/96 MFFD ID space: [6,8]

M1 3F99:1:2FEB:1:5:13:1100::/96 MFFD ID space: [14,16]

Fig. 5. Address reclamation for mobile FFD.

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8

5.1. Analysis of address initialization

T InitRFD ¼ T InitRFDPref ix þ T InitSensor þ T InitUnique

ð18Þ

According to Section 3.3.1, the address initialization cost C InitFFFD of a fixed FFD is made up of two parts, namely the global network prefix acquisition cost C InitFFFDPref ix and the FFFD ID acquisition cost C InitFFFDID , as shown in formulae (1)–(3) where n1 is the number of the neighbor configured fixed FFDs, c is the cost of transmitting a frame between two neighbor nodes and h is the distance between two neighbor nodes. The address initialization delay T InitFFFD of a fixed FFD is made up of the global network prefix acquisition delay T InitFFFDPref ix and the FFFD ID acquisition delay T InitFFFDID , as shown in formulae (4)–(6) where t is the delay of transmitting a frame between two neighbor nodes.

T InitRFDPref ix ¼ t Uh

ð19Þ

According to Section 3.4.1, the address configuration cost C Conf FFFD of a fixed FFD is equal to C InitFFFD , as shown in formula (21). The address configuration delay T Conf FFFD of a fixed FFD is equal to T InitFFFD , as shown in formula (22).

C InitFFFD ¼ C InitFFFDPref ix þ C InitFFFDID

ð1Þ

C Conf FFFD ¼ C InitFFFD

ð21Þ

C InitFFFDPref ix ¼ n1 U c U h

ð2Þ

T Conf FFFD ¼ T InitFFFD

ð22Þ

C InitFFFDID ¼ 2 c U h

ð3Þ

T InitFFFD ¼ T InitFFFDPref ix þT InitFFFDID

ð4Þ

According to Section 3.4.2, the address configuration cost C Conf MFFD of a mobile FFD is equal to C InitMFFD , as shown in formula (23). The address configuration delay T Conf MFFD of a mobile FFD is equal to T InitMFFD , as shown in formula (24).

T InitFFFDPref ix ¼ n1 U t U h

ð5Þ

C Conf MFFD ¼ C InitMFFD

ð23Þ

T InitFFFDID ¼ 2 t U h

ð6Þ

T Conf MFFD ¼ T InitMFFD

ð24Þ

T InitUnique ¼

ðn3  1Þ U t Uh 2

ð20Þ

5.2. Analysis of address configuration

According to Section 3.3.2, the address initialization cost C InitMFFD of a mobile FFD is made up of three parts, namely the global network prefix acquisition cost C InitMFFDPref ix , the MFFD ID acquisition cost C InitMFFDID and the sensor ID setting cost C InitSensor , as shown in formulae (7)–(10) where n2 is the number of the neighbor configured mobile FFD. The address initialization delay T InitMFFD of a mobile FFD is made up of the global network prefix acquisition delay T InitMFFDPref ix , the MFFD ID acquisition delay T InitMFFDID and the sensor ID setting delay T InitSensor , as shown in formulae (11)–(14) where T1 is the sensor ID setting delay.

According to Section 3.4.3, the address configuration cost C Conf RFD of an RFD is made up of three parts, namely the global network prefix acquisition cost C Conf RFDPref ix which is equal to C InitRFDPref ix , the sensor ID setting cost C Conf Sensor which is equal to C InitSensor , and the address uniqueness cost C Conf Unique , as shown in formulae (25)–(28). The address configuration delay T Conf RFD of an RFD is made up of three parts, namely the global network prefix acquisition delay T Conf RFDPref ix which is equal to T InitRFDPref ix , the sensor ID setting delay T Conf Sensor which is equal to T InitSensor , and the address uniqueness delay T Conf Unique , as shown in formulae (29)–(32).

C InitMFFD ¼ C InitMFFDPref ix þC InitMFFDID þ C InitSensor

ð7Þ

C Conf RFD ¼ C Conf RFDPref ix þ C Conf Sensor þ C Conf Unique

ð25Þ

C InitMFFDPref ix ¼ ðn1 þ n2Þ Uc U h

ð8Þ

C Conf RFDPref ix ¼ C InitRFDPref ix

ð26Þ

C InitMFFDID ¼ 2 c Uh

ð9Þ

C Conf Sensor ¼ C InitSensor

ð27Þ

C InitSensor ¼ 0

ð10Þ

C Conf Sensor ¼ n3 U c Uh

ð28Þ

T InitFFFD ¼ T InitMFFDPref ix þ T InitMFFDID þ T InitSensor

ð11Þ

T Conf RFD ¼ T Conf RFDPref ix þ T Conf Sensor þ T Conf Unique

ð29Þ

T InitMFFDPref ix ¼ ðn1 þn2Þ U t U h

ð12Þ

T Conf RFDPref ix ¼ T InitRFDPref ix

ð30Þ

T InitMFFDID ¼ 2 t Uh

ð13Þ

T Conf Sensor ¼ T InitSensor

ð31Þ

T InitSensor ¼ T1

ð14Þ

T Conf Unique ¼ n3 U t U h

ð32Þ

According to Section 3.3.3, the address initialization cost C InitRFD of an RFD is made up of three parts, namely the global network prefix acquisition cost C InitRFDPref ix , the sensor ID setting cost C InitSensor , and the address uniqueness cost C InitUnique , as shown in formulae (15)–(17) where n3 is the number of the RFDs in a WBAN. The address initialization delay T InitRFD of an RFD is made up of the global network prefix acquisition delay T InitRFDPref ix , the sensor ID setting delay T InitSensor , and the address uniqueness delay T InitUnique , as shown in formulae (18)– (20). C InitRFD ¼ C InitRFDPref ix þ C InitSensor þ C InitUnique

ð15Þ

C InitRFDPref ix ¼ c U h

ð16Þ

C InitUnique ¼

ðn3  1Þ Uc U h 2

ð17Þ

5.3. Analysis of address reclamation According to Section 4.1, the address reclamation cost C ReclaFFFD of a fixed FFD is made up of the FFFD ID reclamation cost C ReclaFFFDID and the entry merging cost C Entrymerging , as shown in formulae (33)–(35) where d is the network diameter. The address reclamation cost and delay of a fixed FFD located in the middle of the network tend to be close to the average address reclamation cost and delay, and the distance between this fixed FFD and the AR tends to be d/2. The address reclamation delay T ReclaFFFD of a fixed FFD is made up of the FFFD ID reclamation delay T ReclaFFFDID and the entry merging delay T Entrymerging , as shown in formulae (36)–(38) where T2 is the entry merging delay. C ReclaFFFD ¼ C ReclaFFFDID þ C Entrymerging

ð33Þ

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ð34Þ

C Entrymerging ¼ 0

ð35Þ

T ReclaFFFD ¼ T ReclaFFFDID þ T Entrymerging

ð36Þ

T ReclaFFFDID ¼ t U d

ð37Þ

T Entrymerging ¼ T2

ð38Þ

According to Section 4.2, the address reclamation cost C ReclaMFFD of a mobile FFD is made up of the MFFD ID reclamation cost C ReclaMFFDID and the entry updating cost C Entryupdating , as shown in formulae (39)–(41). The address reclamation delay T ReclaMFFD of a mobile FFD is made up of the MFFD ID reclamation delay T ReclaMFFDID and the entry updating delay T Entryupdating , as shown in formulae (42)–(44) where T3 is the entry updating delay. ð39Þ

C ReclaMFFDID ¼ 2 c U d

ð40Þ

C Entryupdating ¼ 0

ð41Þ

T ReclaMFFD ¼ T ReclaMFFDID þ T Entryupdating

ð42Þ

T ReclaMFFDID ¼ 2 U t Ud

ð43Þ

T Entryupdating ¼ T3

ð44Þ

This scheme uses the sensor IDs to achieve the address configuration for an RFD, so it does not need to perform the address reclamation. Therefore, the address reclamation cost C ReclaRFD and delay T ReclaRFD of an RFD are zero, as shown in formulae (45) and (46). C ReclaRFD ¼ 0

ð45Þ

T ReclaRFD ¼ 0

ð46Þ

6. Simulation We adopt ns-2 to simulate this scheme, and the simulation parameters are shown in Table 3. 6.1. The effect of n1 on address configuration The address initialization process for a fixed FFD or a mobile FFD is the same as the address configuration process, so only the address initialization process is discussed. When n2 is set to 6 and n3 is set to 2, the address configuration cost and delay are shown in Figs. 6 and 7. In Figs. 6 and 7, the address configuration cost and delay for a fixed FFD or a mobile FFD grow with the increase in n1, and the cost and delay for an RFD is hardly affected by n1 and tends to keep stable. The cost and delay for a mobile FFD are maximum, and the ones for an RFD are minimum. During the

Table 3 Parameters. Parameter description

Parameter value

Mobility model Maximum speed Speed angle Pause time Routing protocol MAC protocol Rounds Simulation time

Random walk (Camp et al., 2002) 5 m/s [0,2π] 10 s AODV IEEE 802.15.4 10 600 s

20 15 10 5 0

2

3

4

5

6

n1 Fig. 6. Address configuration cost based on n1.

Fixed FFD address init-analysis Fixed FFD address init-simulation M obile FFD address init-analysis M obile FFD address init-simulation RFD address init-analysis RFD address init-simulation RFD address conf-analysis RFD address conf-simulation Address configuration delay(ms)

C ReclaMFFD ¼ C ReclaMFFDID þC Entryupdating

Fixed FFD address init-analysis Fixed FFD address init-simulation M obile FFD address init-analysis M obile FFD address init-simulation RFD address init-analysis RFD address init-simulation RFD address conf-analysis RFD address conf-simulation Address configuration cost

C ReclaFFFDID ¼ c þ c U d=2

9

150

100

50

0 2

3

4 n1

5

6

Fig. 7. Address configuration delay based on n1.

address configuration process, an RFD must listen to the RFDs in the same WBAN to acquire an inner ID, so the cost and delay are more than the ones in the address initialization process. 6.2. The effect of n2 on address configuration When n1 is set to 3 and n3 is set to 2, the address configuration cost and delay are shown in Figs. 8 and 9. In Figs. 8 and 9, the address configuration cost and delay for a mobile FFD grow with the increase in n2, and the cost and delay for a fixed FFD or an RFD are hardly affected by n2 and tend to keep stable. The cost and delay for a mobile FFD are maximum, and the ones for an RFD are minimum. During the address configuration process, the cost and delay are more than the ones in the address initialization process. 6.3. The effect of n3 on address configuration When n1 is set to 3 and n2 is set to 6, the address configuration cost and delay are shown in Figs. 10 and 11. In Figs. 10 and 11, the address configuration cost and delay for an RFD grow with the increase in n3, and the cost and delay for a fixed FFD or a mobile FFD are hardly affected by n3 and tend to keep stable. When n3 is less than 4, the cost and delay for an RFD

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Fixed FFD address init-analysis Fixed FFD address init-simulation M obile FFD address init-analysis M obile FFD address init-simulation RFD address init-analysis RFD address init-simulation RFD address conf-analysis RFD address conf-simulation

Fixed FFD address init-analysis Fixed FFD address init-simulation M obile FFD address init-analysis M obile FFD address init-simulation RFD address init-analysis RFD address init-simulation RFD address conf-analysis RFD address conf-simulation Network merging delay(ms)

Address reclamation cost

20 15 10 5 0 6

7

8 n2

9

150 120 90 60 30 0

10

1

Fig. 8. Address configuration cost based on n2.

3 n3

4

5

Fig. 11. Address configuration delay based on n3.

Fixed FFD address init-analysis Fixed FFD address init-simulation M obile FFD address init-analysis M obile FFD address init-simulation RFD address init-analysis RFD address init-simulation RFD address conf-analysis RFD address conf-simulation

Fixed FFD address reclamation-analysis Fixed FFD address reclamation-simulation M obile FFD address reclamation-analysis M obile FFD address reclamation-simulation RFD address reclamation-analysis RFD address reclamation-simulation

200 25

150 100 50 0

6

7

8 n2

9

10

Address reclamation cost

Address reclamation delay(ms)

2

20 15 10 5 0 6

-5

7

8

9

10

d

Fig. 9. Address configuration delay based on n2.

Fig. 12. Address reclamation cost based on d.

Fixed FFD address reclamation-analysis Fixed FFD address reclamation-simulation M obile FFD address reclamation-analysis M obile FFD address reclamation-simulation RFD address reclamation-analysis RFD address reclamation-simulation

Fixed FFD address init-analysis Fixed FFD address init-simulation M obile FFD address init-analysis M obile FFD address init-simulation RFD address init-analysis RFD address init-simulation RFD address conf-analysis RFD address conf-simulation

Network merging cost

15 10 5 0

1

2

3

4

5

n3 Fig. 10. Address configuration cost based on n3.

are minimum. When n3 is more than 4, the cost and delay for a fixed FFD are minimum. During the address configuration process, the cost and delay for an RFD are more than the ones in the address initialization process.

Address reclamation delay(ms)

250

20

200 150 100 50 0 -50

6

7

8

9

10

d Fig. 13. Address reclamation delay based on d.

6.4. The effect of d on address reclamation When d ranges from 6 to 10, the address reclamation cost and delay are shown in Figs. 12 and 13.

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In Figs. 12 and 13, the address reclamation cost and delay for a fixed FFD or a mobile FFD grow with the increase in d, and the cost and delay for an RFD are hardly affected by d and tend to be zero. A mobile FFD can move freely, so the address reclamation cost and delay for a mobile FFD are more than the ones for a fixed FFD. In the analysis of the address reclamation for a mobile FFD, it is assumed that the distance between a mobile FFD and a fixed FFD with the same global network prefix and FFFD ID is equal to d. However, in the simulation process, this distance is usually less than d, so the address reclamation cost and delay in the simulation are less than the ones in the analysis.

Address configuration delay(ms)

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11

Proposed Existing stateful Existing stateless 200 150 100 50 0 75×75

6.5. Comparison

105×105 129 ×129 Simulation area(sq.m.)

149×149

Fig. 15. Address configuration delay based on simulation area.

We compare this scheme with a stateful address configuration scheme (Talipov et al., 2011) and a stateless address configuration scheme (Wang and Qian, 2012). These two schemes are selected due to the following reasons:

Address reclamation cost

In the initial stage, the fixed FFD density is set to 0.003/sq m, the mobile FFD density is set to 0.006/sq m, and n3 is set to 2. The number of the nodes is 50, 100, 150 and 200, and the corresponding network area in sq m is 75  75, 105  105, 129  129 and 149  149, respectively. When the communication radius is 20 m, the address configuration and address reclamation comparisons are shown in Figs. 14–17. When the node density and communication radius keep constant, the number of a node's neighbors tends to be stable. As a result, the address configuration cost and delay for a fixed FFD, a mobile FFD or an RFD are also stable, so the average cost and delay also tend to be steady, as shown in Figs. 14 and 15. When the simulation area grows, the network radius increases. Therefore, the address reclamation cost and delay for a fixed FFD or a mobile FFD also increase. Since the address reclamation cost and delay for an RFD tend to be zero, the average address reclamation cost and delay grow with the increase in the simulation area, as shown in Figs. 16 and 17. When the simulation area is 105  105 sq m, the address configuration and address reclamation comparisons are shown in Figs. 18–21.

10 8 6 4 2 0 75×75

105×105 129 ×129 Simulation area(sq.m.)

Proposed Existing stateful Existing stateless 120 100 80 60 40 20 0 75×75

105×105

Fig. 17. Address reclamation delay based on simulation area.

Address configuration cost

Address configuration cost

15 10 5 0 129 ×129

149×149

Proposed Existing stateful Existing stateless

20

105×105

129 ×129

Simulation area(sq.m.)

Proposed Existing stateful Existing stateless

75×75

149×149

Fig. 16. Address reclamation cost based on simulation area.

Address reclamation delay(ms)

1) The scheme (Talipov et al., 2011) has better performance than the stateful address configuration standard, and the scheme (Wang and Qian, 2012) has better performance than the typical stateless configuration scheme MANETConf. 2) These two schemes are based on 6LoWPAN and they both discuss the address reclamation algorithms.

Proposed Existing stateful Existing stateless

149×149

Simulation area(sq.m.) Fig. 14. Address configuration cost based on simulation area.

30 25 20 15 10 5 0 15

20

25

30

Radius(m) Fig. 18. Address configuration cost based on radius.

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Address configuration delay(ms)

12

a mobile FFD's address in a WBAN can be guaranteed without performing DAD or storing the address allocation information, so the average address configuration cost and delay are relatively low. 2) The physical parameters are used to achieve the address configuration, so the address configuration cost and delay are reduced. 3) The address configuration can be achieved without storing the address allocation information, so the address space can be automatically reclaimed without any operations. In this way, the average address reclamation cost and delay are reduced.

Proposed Existing stateful Existing stateless 200 150 100 50 0 15

20

25 Radius(m)

30

Fig. 19. Address configuration delay based on radius.

In this paper, we have looked into the stateful and stateless address configuration approaches for wireless networks. Based on the observation that the stateful and stateless configuration solutions increase the addressing cost and delay, we are motivated to make use of physical parameters collected to achieve the address configuration, and propose an address configuration scheme for a 6LoWPAN-based WBAN to reduce the addressing cost and delay. Finally, the proposed scheme is analyzed and evaluated to justify its advantages. In our future work, we are going to implement this scheme in the hardware environment.

Address reclamation cost

Proposed Existing stateful Existing stateless 10 8 6 4 2 0 15

20 25 Radius(m)

30 Acknowledgments

Fig. 20. Address reclamation cost based on radius.

Address reclamation delay(ms)

7. Conclusion

This work is supported by National Natural Science Foundation of China (61202440) and Jiangsu Provincial Natural Science Foundation (BK20141230).

Proposed Existing stateful Existing stateless 100

References

80 60 40 20 0 15

20

25

30

Radius(m) Fig. 21. Address reclamation delay based on radius.

When the node density keeps constant, the number of a node's neighbors grows with the increase in the communication radius. Therefore, the address configuration costs and delays for a fixed FFD or a mobile FFD increase. As a result, the average address configuration cost and delay also grow with the increase in the communication radius, as shown in Figs. 18 and 19. When the communication radius grows, the network diameter decreases. Therefore, the address reclamation cost and delay for a fixed FFD or a mobile FFD decrease, so the average cost and delay also reduces, as shown in Figs. 20 and 21. From Figs. 14–,21, it can be seen that this scheme has better performance than the existing stateful and stateless schemes. The main reasons are analyzed as follows: 1) The node type is included in the address structure to differentiate a mobile FFD from an RFD. In this way, the uniqueness of

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Please cite this article as: Wang X, et al. A novel IPv6 address configuration for a 6LoWPAN-based WBAN. Journal of Network and Computer Applications (2015), http://dx.doi.org/10.1016/j.jnca.2015.10.013i