2276 IEEE Transactions on Consumer Electronics, Vol. 56, No. 4, November 2010 Soft Handover Mechanism Based on RTP Parallel Transmission for Mobile IPTV Services Qi Qi, Yufei Cao, Tonghong Li, Xiaomin Zhu, Jingyu Wang Abstract — Mobile Internet Protocol Television (IPTV) technologies including Wideband Code Division Multiple provides users with multimedia content through wireless Access (WCDMA), Wireless Local Area Network (WLAN), access technologies whenever they want and wherever they and World Interoperability for Microwave Access (WiMAX) are. However, vertical handover in heterogeneous networks etc. When users move among these networks, the continuity results in long interruption time and large packet loss rate, of the services should be guaranteed with neither disruption which poses a challenge for seamless mobile IPTV service. nor perceptible degradation. Thus, the mobility management is The existing solutions that make use of the heterogeneous the key point to provide seamless mobile IPTV service. access networks to transmit multimedia content have two Moreover, as the wireless networks have limited resources drawbacks: high bandwidth consumption of the wireless compared to wired networks, overall bandwidth consumption networks and lots of packets loss when a user resides in the needs to be minimized. Although the vertical handover has overlapped area of the boundary. To solve these issues, we been a research subject for several years, it still poses a propose a new soft handover mechanism, based on the IPTV challenge for mobile IPTV service as it typically causes long server and the consumer electronic devices. The proposed handover delay, high packet loss rate and wireless bandwidth Parallel Soft Handover (PSH) divides the Real-time Transport waste. Protocol (RTP) packets according to the packet loss rates, and exploits different networks efficiently by using parallel Fig.1 presents a scenario in which the mobile IPTV service transmission. Moreover, the selective retransmission for RTP is provided in heterogeneous networks. A user moves across packets is introduced to reduce the packet loss. Simulation several networks and several areas covered by different results demonstrate that the PSH can reduce the packet loss wireless access technologies when the IPTV program is rate, as well as obtain a more efficient use of the wireless playing. Before handover takes place, the link to the WCDMA bandwidth1. network (old path) and the link to the WiMax network (new path) are both available. Also, when the user enters the house Index Terms — mobile IPTV, handover, parallel transmission, that is covered by WLAN, the mobile device can explore the heterogeneous networks. paths of the WCDMA and WLAN in parallel to receive the multimedia content. I. INTRODUCTION The rapid growth of wireless access technologies and the increasing number of mobile consumer electronic devices have led to a considerable increase of the users’ demand for mobile networking services. The mobile Internet Protocol Television (IPTV) extends many IPTV services to mobile users, which enables them to receive multimedia traffic such as TV signals, video, audio, text, and graphics, through IP- based networks, whenever they want and wherever they are [1]. In the overlapped heterogeneous networks, the mobile devices can receive the multimedia content by multiple access 1 This work was jointly supported by: (1) National Natural Science Foundation of China (No. 60902051); (2) the Fundamental Research Funds for the Central Universities (BUPT2009RC0505). Qi Qi is with State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications; Beijing, Fig. 1. Vertical handover of IPTV service P.R. China, 100876 (e-mail: [email protected]). Tonghong Li is with the department of computer science, Technical University of Madrid, Madrid, Spain, 28660 (e-mail: [email protected]). Due to the increase of CPU performance and memory Yufei Cao is with EBUPT Information Technology Co., Ltd.; Beijing, P.R. capacity, it is possible to have the capability of media China, 100083 (e-mail: caoyufei@ ebupt.com). processing in mobile devices. In this paper, we propose a Xiaomin Zhu is with State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications; Beijing, terminal driven handover method for mobile IPTV service to P.R. China, 100876 (e-mail: [email protected]). utilize the two network bandwidth and avoid packets loss Jingyu Wang is with State Key Laboratory of Networking and Switching when a user moves in heterogeneous networks. This proposed Technology, Beijing University of Posts and Telecommunications; Beijing, P.R. China, 100876 (e-mail: [email protected]). Parallel Soft Handover (PSH) is based on RTP parallel Contributed Paper transmission, which splits a RTP packet into two parts and Manuscript received 10/12/10 Current version published 12/23/10 Electronic version published 12/30/10. 0098 3063/10/$20.00 © 2010 IEEE Q. Qi et al.: Soft Handover Mechanism Based on RTP Parallel Transmission for Mobile IPTV Services 2277 transmits them in parallel via the old and new paths during the [8] present a Session Initiation Protocol (SIP) based mobility vertical handover. Comparing with the existing approaches, management mechanism by making use of the Session Border PSH makes the following three contributions to mobile IPTV Controllers (SBC). The SBC duplicates the RTP packets and services: (i) PSH splits a large payload Real-time Transport sends them to the new and the old interface in separate. Protocol (RTP) packet into two smaller sub-packets and In the state-of-the-art soft handover mechanism for mobile retransmits some of the lost sub-packets so as to decrease the streaming media transmission, duplicate packets are packet loss rate. This is very useful when a user resides in the transmitted via the two paths before the old path breaks [7] overlapped area of the boundary between two access [8], so the packet loss rate is reduced comparing with the networks, where the wireless signals of two links are quite “make before break” handover [2]. But the duplicate poor. (ii) PSH utilizes the wireless network resources more multimedia content transmission by the soft handover may efficiently by sending different media data via the new and the degrade the network performance. This is particularly a old paths simultaneously. (iii) All modifications are restricted challenge when the user stays for a long time in the to the mobile devices and IPTV servers, and the proposed overlapped area of two networks as the IPTV multimedia technique is fully interoperable with existing IPTV service content always contains large RTP packets. In order to infrastructure, so it can be easily deployed. improve the network performance, two paths are exploited to The remainder of this paper is organized as follows. Section transmit the splitting media flows under load balance [3]. II surveys related work. Section III proposes the RTP parallel When the Frame Error Rates (FERs) of the two links become transmission algorithm in the PSH. Section IV introduces the higher, however, the feasibility of splitting transmission simulation model and investigates the performance of PSH. between the old and the new path is undermined greatly. Finally, conclusions are described in Section VI. Accordingly, we propose a new soft handover mechanism which enhances the RTP processing capability in the mobile II. RELATED WORK device to reduce the packet loss rate and make better use of For the mobile IPTV services, Jeon et al. [2] propose a two networks at the same time. mobile multicasting model based on Proxy Mobile IPv6 (PMIPv6). The new fast handover scheme realizes the “make III. SOFT HANDOVER MECHANISM FOR MOBILE IPTV before break” handover procedure by predicting users’ A. The Architecture and Enhanced Functionalities direction of movement and transferring the context message before the handover execution. Ciubotaru et al. [3] propose a We assume that when a mobile IPTV device performs a Smooth Adaptive Soft Handover Algorithm (SASHA) for vertical handover, it can dynamically configure its IP address mobile IPTV services. The algorithm splits the transmission of from the new wireless network in advance. media flows based on load balancing between two different networks according to their quality of service (QoS) metrics. Some methods have been proposed to improve the streaming media system for supporting mobile users. Lee et al. [4] address a movement-aware vertical (MAV) handover algorithm between WLAN and WiMAX for seamless ubiquitous access. The MAV algorithm adjusts the dwell time adaptively and predicts the residual time in the cell of target Base Station (BS). Kim et al. [5] propose an efficient video streaming method, which dynamically adjusts the video transmission rate based on the channel bandwidth and Fig. 2. Protocol architecture for PSH minimizes the error propagation during handover. Pyun et al. [6] proposes a new cross-layer streaming video system for Fig. 2 shows our enhanced functionalities above the vertical handoff. The TCP Friendly Rate Control (TFRC) standard RTP and the Real-time Control Protocol (RTCP) server uses explicit vertical handoff messages for faster rate stack in IPTV server and mobile device. In the IPTV server, adaptation to a new target network, and the TFRC client RTP packet splitter and Link status analyzer are two new determines the switching time between different networks components for PSH mechanism. The RTP packet splitter according to the handoff metrics. divides each RTP packet into two parts according to the On the other hand, researches on the optimization of performance of both networks and sends them via the old and handover control for seamless session handover are currently the new paths respectively. The Link status analyzer collects in progress. Banerjee et al. [7] firstly introduce a SIP-based the network performance parameters from the RTCP Receiver architecture to support soft handover for IP-centric wireless Report (RR) messages, and calculates the average packet loss networks. At the BS of the old network, the packet replicator rate.