SIP-Based Internetwork System Between Future IP Networks and ...

2012 4th Computer Science and Electronic Engineering Conference (CEEC)

University of Essex, UK

SIP-Based Internetwork System Between Future IP Networks and ZigBee Based Wireless Personal Area Networks (WPAN) Mazin Alshamrani, Haitham Cruickshank, Zhili Sun, Basil Elmasri, and Vahid Heydari Tafreshi, (Members IEEE) Centre for Communication System Research (CCSR), University of Surrey, Guildford, Surrey, GU2 7XH, UK e-mails: [email protected], [email protected], [email protected], [email protected], [email protected]

Abstract—The internetwork system between Future IP Networks and ZigBee Wireless Networks has two main approaches; the SIP Proxy Based approach, and the ZigBee Stack Based approach. Because of the dynamic nature of the ZigBee devices, both approaches need to be improved to support the connectivity system and the Quality of Service (QoS) for different types of sensing and actuating applications. This paper proposes an initial design for a modified version of SIP (Mod-SIP) for ZigBee Stack Based approach. In addition, the paper introduces the Combined Approach which is an enhanced internetwork system used to provide more reliable and flexible connectivity system between ZigBee WPANs, and the IP clouds. An initial design and simulation efforts on OPNET implemented to study the current approaches and compare it with the proposed approaches. It shows that the SIP Proxy Based approach is not efficient for Future IP Networks applications as it has a high rate of End-toEnd delays because of the lack of flexibility between SIP signaling system and the ZigBee WPANs. The initial investigations shown that the Combined approach can provide more reliable connectivity system with the support for the QoS for different types of instantaneous applications such as VoIP and video conferencing. Index Terms— SIP, ZigBee, WPAN, WSN, Future IP Networks, QoS, VoIP

I. INTRODUCTION Today’s network systems are trying to provide wide range of services and applications over different types of platforms and communication systems. Number of research efforts had been taken to employ the IP layer as a common access medium between Future IP networks and different types of network systems. The Session Initiation Protocol (SIP) is one of the invented IP-Based solutions that provide simple connectivity over the application layer and it is extensively used in Future IP Network systems. SIP depends on the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) interactions between different types of network systems for reliable and unreliable applications and services such as VoIP, online conferences, web streaming, large data transferring, etc [1]. On the other hand, ZigBee Based network system is a growing wireless technology with limited power resources and network capabilities that provides wide range of supportive remote sensing, monitoring, and actuating services for different types of environmental applications that need to interact with other network systems over the IP clouds [2]. ZigBee technology designed to support Low Rate Wireless Private Area Networks (WPAN) based on the IEEE 802.14.52003 standard.

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A. SIP Overview SIP is a signaling protocol defined by SIP Working Group, within Internet Engineering Task Force (IETF). The protocol was published as IETF (RFC 2543) and currently has the status of a proposed standard [3]. SIP is commonly used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP). SIP sessions can involve one or more participants and can be used for creating, modifying and terminating two participants (unicast) or multi participants (multicast) sessions by consisting of one or several media streams. SIP is a text-encoded protocol with a built in ability to modify and extend its features. The modification approaches could apply on addresses or ports adoptions, participant invitations, and adding or deleting media streams [1]. SIP depends on the supported Internet protocols, and it includes many elements of the Text-Based protocols. Moreover, SIP protocol is an Application Layer protocol designed to be independent of the existing transport layer and it can run on top of TCP/IP, UDP/IP, or Stream Control Transmission Protocol (SCTP) [2]. This important characteristic allows SIP protocol to provide various features and services for the network systems such as call control services, mobility, interoperability with existing telephony systems, and more. The SIP Server is a SIP-Based server consists of three servers: proxy server, registrar server, and redirect server. B. Wireless ZigBee Overview The ZigBee specified a set of high level communication protocols that designed to be simpler and less expensive than other WPANs such as Bluetooth. It uses small and low power digital radios that target the radio frequency (RF) applications with low data rate, low-cost, long battery life (5 to 10 years), and wireless secured mesh network system. These features allow the technology to be widely deployed in different types of wireless control and monitoring applications such as home automation, smart energy, telecommunication services, health care, remote control, etc. As a result of the nature of ZigBee features and capabilities, number of limitations and challenging issues are there such as the coverage ranges (100 to 300 meters), low power resources, maximum throughput of 250 kbps, synchronization, interactions with other network systems, etc. From the communication respects, there are two types of ZigBee devices, the Full Functional Devices (FFD) and the Reduced Functional Devices (RFD). The FFD has a full construction of the ZigBee model over the Network and

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2012 4th Computer Science and Electronic Engineering Conference (CEEC)

Mod SIP

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the Application layer, and it can work as a ZigBee WPAN coordinator or Gateway with other network systems. On the other hand, the RFD has limited capabilities over the application layer, and it cannot be implemented as a ZigBee WPAN coordinator or Gateway. Figure 1 (Left) illustrate the ZigBee protocol stack of FFD compared with the Open Systems Interconnection (OSI) Model. It shows that ZigBee does not support the TCP/UDP Transport layer where the Application layer interact with the Network layer for specific defined types of applications as a result of the modest capabilities of the microprocessor and the memory size of ZigBee devices. Figure 1 (Right) shows the ZigBee frame structure where the maximum size of the ZigBee frame is 127 Bytes, including all the headers’ information [2]. The principal objectives of Application layer are the realization of the network communication between different devices, and applications to access the information services, the calls of the application layer protocols for continuous and discrete control applications and support services. The main component of the application layer is the application support Sub-Layer (APS) which provides a well-defined interface and control services between the user applications and ZigBee devices.

[---- Preamble ----]

Figure 1: The OSI Model for the Gateways and SIP Servers compared with the ZigBee Protocol Stack for Full Functional Device (FFD) (Left), ZigBee frame Structure (Right)

II. BACKGROUND There are number of research efforts that tried to provide adaptable approaches to link different types of network systems and entities together depending on the IP-Based internetwork system. Some studies used to develop new solutions and implementations more than studying and evaluating these suggested approaches. In addition, most of the available few studies are related to other research areas that focused on providing solutions for certain applications or services by enhancing the network components and technologies to work together without the concerns about the networking efficiency factors. In general, the SIP Based internetworking systems between Future IP Networks and wireless ZigBee network are depending on two main approaches [4], the SIP Proxy Based approach, and the ZigBee Stack Based Approach. The main provided approaches and applications focused on the internetworking with IP Multimedia Subsystem (IMS) using the SIP Proxy Based Approach. However, the investigations in this research area still modest, and the SIP Based internetwork system over ZigBee need to have an effective interaction system to support

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SIP/TCP and SIP/UDP applications. A. Related Research Efforts In [5], a proposed approach that used to enable homogeneous communications between heterogeneous distributed entities using SIP protocol as a universal communication bus to link different types of computing and network systems, including Serial-Based sensors. In [6] an investigation about the internetwork between heterogeneous networks and wireless ZigBee network used to employ the SIP protocol system to provide unified SIP messaging concepts used by many components as in the presence service between the heterogeneous network systems, and the discovery and binding concepts of ZigBee. In [7] an approach for WSN deployment based on the integration of the TCP/IP network with the ZigBee network system used to provide a TCP/IPZigbee Bridge architecture over the ZigBee applications. A reliable data transmission system used to hold and analyze various physiological data collected from ZigBee Based healthcare monitoring system proposed by [8]. This system used to manage and access large number of ZigBee devices with multiple users as well as different types of application. The proposed system applied and implemented the access control system with a reliable data transmission on the upper layer of the ZigBee devices, the Application Layer, by using a group ID mechanism for each ZigBee cluster, application, and user. The researchers in [9] described how SIP, Zigbee and WLAN technologies could be integrated together to support mobility and event management in medical environments. In [10], a proposed and implemented system to support mobile video conference based on the forwarding sessions of SIP protocol and Zigbee sensors. They applied the mobile video conference system which includes subsystem blocks which are the Network Video Phone Service (NVPS), the Network Sensor Control (NSC) blocks, the SIP Service device, and the video conference device with GUI for end users. A developed application prototype used to illustrate the TinySIP as a modified version of SIP over ZigBee devices for a automated healthcare processes in hospitals with WLANs [11]. A proposed Emergency Communication System based on Wireless Mesh Network (ECS-WMN) by [12] that depends on the multi-hop wireless communication and personal communication systems based on VOIP and SIP, video applications, and sensor monitoring, which all can interact together using WiFi and Zigbee mesh systems. A framework based on SIP/ZigBee architecture proposed in [13] by using SIP and its extensions to provide seamless convergence of traffic measurement and control network between Internet and short-range wireless sensor and actuator networks (WSAN) can be achieved. However, no details provided about the signal interactions of SIP over ZigBee and no implementations of the proposed system. B. SIP Proxy Based Approach This approach is the only available internetwork system that could be implemented in the real world. However, it is not efficient for multimedia services over the ZigBee devices.

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2012 4th Computer Science and Electronic Engineering Conference (CEEC)

Figure 2 shows a simple illustration for an internetwork system between simple ZigBee WPAN and a remote user (Monitor) over Internet clouds. The remote user needs to register with the SIP registrar server to verify himself with unique identifiers that used temporarily, maintained regularly, used for the mapping purposes, and known as the Uniform Resource Identifiers (URI). The routing system which based on the URI is using an intermediate SIP proxy, location and redirect servers as part of the session setup process. The presence server provides a database for the URIs of the active applications in both sides of the Future IP networks, the IDs of the ZigBee WPANs clusters, and the requested binding messages. The SIP Proxy Based interconnection of SIP/ZigBee depends on the presence server to provide a dynamic and instantaneous access to the ZigBee WPAN cluster collected data. The data flows between the Gateway and the ZigBee WPAN cluster devices are running over the ZigBee signaling system as shown in Figure 3 over the SIP interconnection stages.

Figure 2: A simple illustration for the SIP Proxy Based approach

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abstracted and modified SIP over ZigBee network systems. The TinySIP originally designed to provide the SIP signaling between ZigBee WPAN nodes and Wireless Local Area Networks (WLAN) regardless of other network systems. The SIP signaling system between both sides used to be translated to TinySIP. For local and small private networks, the SIP proxy server is only required for the system to provide the connectivity with the ZigBee nodes. As ZigBee doesn’t support the transport layer, it provides the functionality of the application layer by using SIP/TinySIP translator on the FFDs nodes and the ZigBee WPAN Gateways to support the SIP interactions with the ZigBee IP/Network layer. III. MOD-SIP INITIAL DESIGN As there is no real implementations for the ZigBee Based approach internetwork system between Future IP Networks and ZigBee WPANs, the Modified-SIP is proposed to provide this type of internetwork system. The Modified-SIP (ModSIP) is an abstracted and adjustable SIP signaling system designed to provide the SIP connectivity between Future IP Networks and LR-WPAN systems for different types of SIP applications and services. In this paper, Mod-SIP aims to support the SIP internetwork system between Future IP networks and ZigBee networks with low delays, direct connectivity, and better QoS for reliable and real-time applications. Figure 4 shows a simple illustration for an internetwork system between simple ZigBee WPAN using Mod-SIP and a remote user (Monitor) in the other side of the world over Internet clouds. The Presence server is not needed in this system design as the Mod-SIP approach provides a direct instantaneous connectivity system. The signaling system between the Gateway and the FFDs ZigBee WPAN cluster devices are running over the ZigBee signaling system as shown in Figure 5 over the SIP interconnection stages.

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Figure 4: Simple illustration for ZigBee Stack Based approach using Mod-SIP

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Figure 3: The signal flows for the SIP Proxy Based approach

C. ZigBee Based Approach This approach introduced by [11] as a simple design for an

To apply the Mod-SIP, a SIP/Mod-SIP translator needs to be implemented on the FFDs ZigBee nodes' interfaces and Gateways to provide the internetwork system with Future IP Networks. This translator provides light interactions for SIP signaling systems, including the connection control messages, and the QoS negotiation services. Figure 6 shows the representation of SIP/Mod-SIP translator on the ZigBee FFDs devices or the gateways for SIP signals from Future IP Networks to the ZigBee WPANs.

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2012 4th Computer Science and Electronic Engineering Conference (CEEC)

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signals from ZigBee WPANs nodes to the Future IP Networks. The translator receives the Mod-SIP signals then it checks the labeled source and destination of the Mod-SIP frame. The translator will analyze the signal's packets and check the methods and the extensions' indexes from the ModSIP/SIP included library. The SIP signal will be subsequently formed and forwarded to the Application layer of the FFD and then to the destination end of the Future IP Networks. Finally, the SIP/Mod-SIP translator not only supports the ZigBee WPAN systems. It can also support the other types of WPAN network systems.

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Message Message OK OK Mod-SIP: OK ZigBee Ack Packet

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Connection Termination Message (BYE) From The ZigBee Device to The User/Monitor

BYE BYE OK OK Mod-SIP: OK ZigBee Ack Packet

Figure 5: Signal flows for ZigBee Stack Based approach using Mod-SIP

The translator consists of three main components, the signaling analyzer, the Library which works as an index for the SIP/ Mod-SIP methods and extensions, and the converted signals former. The translator receives the SIP signals then it checks the labeled source and destination of the SIP frame. Depending on the signaling type, the translator will analyze the signal's packets and check the methods and the extensions' indexes from the SIP/Mod-SIP included library. The ModSIP/IP signal will be subsequently formed and forwarded to the ZigBee IP layer of FFD and then to the destination node. This translation process needs to support the QoS of the ZigBee Stack Based internetwork system with minimum delays.

Figure 6: SIP/Mod-SIP translator design

The same with the opposite direction of the signaling system, Figure 7 shows the representation of Mod-SIP/SIP translator on the ZigBee FFDs or the gateways for Mod-SIP

Figure 7: Mod-SIP/SIP translator design

IV. THE COMBINED APPROACH The Combined Approach is combining both, the Proxy Based and the ZigBee Stack Based Approaches. It is proposed to improve the SIP/ZigBee internetworking system between the Future IP Networks and the WPANs in general and for the ZigBee WPANs, in particular. In addition, the combined Approach is a solution for the problems of the Proxy Based, and the ZigBee Stack Based approaches to support the QoS of the connectivity system. The Combined Approach proposed to provide a reliable, real-time, and dynamic connectivity system for both, SIP/TCP and SIP/UDP applications. Figure 8 shows a simple illustration for the Combined approach internetwork system between ZigBee WPAN and a remote user (Monitor) over Internet clouds. The SIP registrar server used to verify the users with unique identifiers that temporary used to maintain the SIP networking mapping system. The routing system which based on the URI is using an intermediate SIP proxy, location and redirect servers as part of the session setup process. In this approach, the proxy server will serve the URIs of the active applications for both sides of the Future IP networks and the IDs of the ZigBee WPANs clusters. As Mod-SIP aims to support the SIP system between Future IP networks and ZigBee networks with low delays, direct connectivity, and better QoS for reliable and real-time applications, the Combined Approach is depending on this signaling system. The SIP/Mod-SIP translator implementation is on the FFDs ZigBee nodes, the WPANs Gateways, and the SIP server to support the internetwork system with Future IP Networks. The signaling system of the Combined approach is shown in Figure 9 for the SIP interconnection stages.

209

2012 4th Computer Science and Electronic Engineering Conference (CEEC)

University of Essex, UK

monitoring/detector system between node_0 in the ZigBee WPAN cluster and a remote user/Monitor over the Internet clouds as in Figure 10. The design implemented in OPNET using SIP and ZigBee modules. VoIP used to run over Real Time Transfer Protocol (RTP) / UDP. By examining the Endto-End delay for simple VoIP scenario between the two ends, a high delay (425ms) had shown in Figure 11. This is almost twice the maximum allowed delays for VoIP applications over internet clouds [10] which means that the SIP Proxy Based approach is not efficient for SIP/UDP applications over the ZigBee WPANs network systems. Figure 8: The proposed Combined Approach design

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Figure 10: Simple OPNET simulation model for the SIP Proxy Based internetwork system

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Figure 9: The Signal Flows of the Combined Approach

This approach uses simple direct connection with the coordinator of the ZigBee WPAN cluster to run the WPAN applications and services directly without relying to any middle agent. Furthermore, this design aims to provide a more reliable internetworking system to solve the problems of the connectionless and the single point of failure. The main challenge in this approach is the integration between the SIP Proxy Based, and the ZigBee Stack Based approaches in terms of the compatibility for the internetwork system features and the nature of the WPANs applications. V. INITIAL SIMULATIONS The initial simulation efforts focused on the SIP Proxy Based approach to study and analyze its functionality and performance. The simple network system in Figure 2 is implemented with OPNET simulator Version 16.1 [14]. A simple VoIP application working as continues voice

Figure 11: End-to-End delays for a simple VoIP application using the SIP Proxy Based approach for the OPNET model of Figure 10

VI. APPROACHES COMPARISON Each approach shows different capabilities for the internetwork system between Future IP Networks, and ZigBee Based WPANs. The SIP Proxy approach is currently the only supported and available approach between the two platforms. However, the initial simulations shown problems within the connectivity system as delays accrued in the presence server and the WPAN coordinator node for the SIP/UDP applications as a result of the SIP signals interaction between IP clouds and ZigBee. On the other hand, the ZigBee Stack Based approach

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2012 4th Computer Science and Electronic Engineering Conference (CEEC)

gave a real-time and direct connection between two ends over the Future IP Networks without using the presence server; however, it doesn’t provide any data recovery. The proposed Combined approach is able to solve the main problems of the previous approaches by providing enhanced features of the internetwork system with better QoS over different type of applications. Table 1 summaries the general features of each approach. Proxy Based Approach

ZigBee Stack Based Approach

Combined Approach

The Approach is Available and Supported

Not Available/ Not Supported Yet

Not Available/ Not Supported Yet

Presence Server Required

Presence Server not Required

Presence Server Required

Not Provide Data Recovery (Database) No Single Point of Failure

Provide Data Recovery (Database) No Single Point of Failure

Reliable connection

Weak Reliability

Reliable Connection

Not Real-time Connection

Real-time Connection

Real-time/ Not RealTime Connection

Provide Data Recovery (Database) Single Point of Failure

Table 1: A Comparison between the different features of the approaches of the SIP Based Internetwork system over Future IP Networks and ZigBee Based WPANs

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the main usages of SIP is to support the Future IP Networks QoS, the SIP-Based approaches aim at enhancing the QoS provisioning system for SIP/TCP, SIP/UDP, and data transmission applications over ZigBee WPANs. The initial simulation efforts on OPNET showed that the SIP Proxy Based approach, which used to relay the SIP application through a Presence Server, has a considerable End-To-End delay for SIP/UDP applications such as VoIP. These delays have increased with the growth of the ZigBee WPAN nodes. Furthermore, the initial works shown that VoIP applications are difficult to implement with SIP Proxy Based approach. As a solution, a Mod-SIP signaling system and the Combined approach proposed to support both applications, SIP/TCP and SIP/UDP, such as VoIP as well as video conferencing. In addition, an initial design of the Mod-SIP and the Combined approach had proposed in this paper. The comparisons of the approaches showed that the Combined approach have the ability to solve the connectivity problems of ZigBee WPANs with Future IP Networks. Future works are aiming at design, implement, and evaluate the Mod-SIP translator for the ZigBee Based and the combined approaches for different applications over ZigBee WPANs using OPNET simulation models with more experimental results. REFERENCES [1]

VII. DISCUSSION The ZigBee WPAN nodes are used to collect and monitor various types of data such as images, video, audio, temperature, humidity, etc. The collected data depends on the available supported features of each node. One of the major problems of using ZigBee WPAN within the IP clouds is the lack in the dynamic connectivity with the different components of the network systems. The required optimal capability of the ZigBee WPANs is to make the collected records and facilities accessible by the authorized users from anywhere, at any time, and wherever the ZigBee devices are. The internetwork system of SIP/ZigBee faces a number of barriers mostly related to the nature of the wireless ZigBee networks and its collected data. For example, in small WPAN clusters, there is no massive traffic that could cause congestions or delays in the data transmissions over the ZigBee PAN. As a result, the QoS measurements need to have a real traffic for the distributed wireless ZigBee networks. Big clusters with large number of nodes have real traffics with various network capacities which need to improve its QoS. Thus, SIP/ZigBee QoS studies are required on the admission control, resource allocation, AAA, etc. The proposed Mod-SIP translator and the combined approach support the QoS as SIP is basically used to support the functionalities of interwork systems for different multimedia applications. VIII. CONCLUSION AND FUTURE WORKS The research area of the SIP-Based internetwork system over WPAN in general is still new and needs more research efforts and experiments to support the performance and improve the functionality over Future IP Networks. As one of

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