1 Testbed for Mobile Multimedia over WiMAX

Somsubhra Sharangi and Mohamed Hefeeda School of Computing Science Simon Fraser University Surrey, BC, Canada Email: {ssa121, mhefeeda}@cs.sfu.ca Technical Report

I. INTRODUCTION

Multimedia multicasting to mobile devices has emerged as one of the popular services over upcoming next generation wireless networks. Mobile WiMAX technology specified in IEEE standard 802.16 [1] is a technology which was originally designed for providing last mile wireless broadband access and is now being considered for providing mobile multimedia services. Investigating and analyzing different real life scenarios in these networks is of great importance. Since building a WiMAX multimedia delivery platform is significantly complex, many researchers have resorted to simulation software for conducting their experiments. Although simulation is a good way for preliminary assessment it abstracts many real life details that can significantly impact the performance of the solution. In this article we discuss the design of a mobile multimedia testbed over WiMAX network. The main objective is to use this testbed as a state-of-the-art research platform for investigating different multimedia transmission schemes specific to mobile WiMAX network. Potential applications for the testbed include Video-on-Demand services, Mobile TV services, Mobile Videoconferencing Services, Interactive Multimedia Streaming services, Mobile Gaming services and other upcoming mobile multimedia applications.

II. RELATED WORK

The design of multimedia testbeds has been extensively studied for wire-line environments. For ex- ample, Chang et.al. [2] discuss the design of a multimedia testbed for supporting video on demand services. In the wireless domain, Dutta et. al. [3] describe the implementation of a mobile video-on- demand testbed over WiFi network. The testbed was further extended in [4] to support Internet telephony and streaming multimedia. The works in [3] and [4] are implemented over a local area network and are

February 26, 2010 DRAFT 2 not applicable to a wider area. Broadband wireless access technologies like WiMAX are still in an early stage of mainstream use. Therefore the cost of WiMAX equipment and software is relatively high. Due to the cost factor and the considerable complexity of deploying a wide area network, very few attempts have been made towards construction of a WiMAX testbed in academic settings. An open source WiMAX base station is currently being developed at Rutgers University under the Global Environment for Network Innovation (GENI) [5] project. In another instance, under the WiMAX Extension to Isolated Research Data networks (WEIRD) [6] initiative, four WiMAX research networks have been set up at different European universities. But, so far no WiMAX testbed has been designed focused on mobile multimedia services.

III. BACKGROUND

A. Multimedia Dissemination over WiMAX

We first describe the components of a video streaming system over WiMAX. We start with a system with four entities as displayed in Figure 1a. The first entity is a video content server which receives content from different sources. The sources may include TV programs recorded at studio, live video recording of a event, Internet TV operations and any other future video service. The content is delivered to WiMAX network through the high capacity core network which also performs authentication, authorization and accounting operations. The next component in the system is access service network gateway or ASN-GW which interfaces the WiMAX access network to the core network. ASN-GW is connected to multiple bases station transceivers via a backhaul network links. In each base station the video streams are packetized into MAC PDUs and later into TDD frames. The TDD frames are transmitted to WiMAX subscribers using OFDMA technology. In WiMAX physical layer, data in transmitted over multiple carriers in Time Division Duplex (TDD) frames. Each frame contains header information and user data maps followed by rectangular bursts of user data. Although streaming video can be transmitted in these frames as a uni-cast, multicast, or broadcast service, for transmitting a large number of streams broadcast and multicast are more resource efficient. Since video dissemination is expected to be the prevalent traffic pattern in future networks, the WiMAX standard defines a service called Multicast and Broadcast Service (MBS) in the MAC layer for facilitating broadcast and multicast. Through this service, a certain area in each TDD frame can be set aside for multicast-only or broadcast-only data. In Figure 1b we show a TDD frame with MBS area allocated inside it. The entire frame can also be designated as a download-only broadcast frame. One of the major task of MBS module is to create the MBS data area in each frame and allocate video data to it such that the real time nature of the video stream traffic is maintained.

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(a) (b)

Fig. 1: Multimedia Delivery over WiMAX

B. Goals of the Testbed

Since the testbed is going to be used for academic purposes we aim at achieving high flexibility while still maintaining a reliable depiction of a practical scale network. We set our goals based on the domain on applications to be supported by the testbed. We plan to support emerging rich multimedia applications while maintaining a reasonable backward compatibility with legacy application. For our immediate needs we plan to support a scalable video steaming framework over the WiMAX test network. Scalable video streaming is a demanding application requiring simultaneous capabilities of audio streaming, video streaming and data streaming. Data streaming id required for providing content discovery services to the end user. In near future we plan to extend the network to support other applications like (1) VoIP, (2) mobile video-conferencing, (3) location based multimedia services, (4) mobile gaming, and (5) multimedia rich interactive mobile Internet applications. To support high level of customization options our design should aim for providing controllable inter- faces to the MAC layer of mobile WiMAX stack. Our testbed is aimed at exploring the multimedia specific features like multicast overlay construction, energy efficiency features while offering full flexibility for testing the more fundamental features like throughput,QoS and mobility.

IV. TESTBED ARCHITECTURE

In this section we describe the basic building blocks of our proposed testbed. The Testbed software components are divided into three functional layers, namely, the content management layer, the service management layer and the resource management layer. The content manager deals only with application layer functionality like aggregation of content, generating content metadata etc. The resource management

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(a) (b)

Fig. 2: Content Manager and Service Manager Block Diagram

layer deals with the low level functionality of WiMAX MAC and performs roles of frame construction and radio resource management. The service layer interacts with the content manager and resource manager to facilitate deployment from a service perspective. It provides functionality like subscription management, service management and subscriber specific customization management. In Figure 2 we display the three modules in context of WiMAX stack. Figure 2a gives a high level description while figure 2b describes in more details the mapping of protocols and functionality to the modules.We describe the three components in more details below.

A. Content Manager

The main responsibilities of content manager are (1) providing API for receiving local or remote content, (2) media adaptation functions like trans coding and ad-insertion (3) managing DRM of the content and (4)providing content consumption statistics. The content manager can reside either at the content service provider or the core network service provider’s network.In the content manager the video content is managed and formatted. The content manager interacts with the content providers outside of the WiMAX ASP to obtain content. It handles the DRM related interfaces between the WiMAX ASP and the content provider. Also its provides the necessary interfaces for handling advertise insertion and interactivity. It neither holds any user related information not does it provide any user specific service. In the design of content manager as displayed in Figure 3a we see it interacts with local and remote content providers. Each content provider has might use a different DRM mechanism, a different service meta data (i.e. EPG) and content format. The content manager abstracts these different formats and provides a unified content view to the service manager. The content manager also relays the interactivity information

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(a) (b)

Fig. 3: Content Manager and Service Manager Block Diagram

between the content provider and the service manager. The content manager has an interface with he advertisement server for smooth integration of advertisement into the video content.

B. Service Manager

The second component is the service manager which has the following responsibilities:(1) subscription management (2) network overlay construction for MBS zones (3) mapping of content to WiMAX service flow IDs (4) efficient media routing (5) service flow management and (6)generating service discovery functionality like EPG. The SM also exposes API for the CM to deliver content and provides subscriber usage statistics for billing and accounting purposes. The SM is the entry point to WiMAX network from the content side and it resides on the WiMAX service provider’s network. In the service manager the subscriber details are managed. It interacts with the base station resource manager and receives subscriber register requests and service requests. It then accordingly creates a new service flow or adds the user to an already existing service flow. Then an unique connection is created and communicated to the user via the base station. Once the connection has been established the data path is set up from the content manager to the subscriber station. A simple service manager is described in figure 3b. The service manager maintains a database of the subscribers and their profiles. It also maintains a list of the contents and their QoS requirements. It customizes the EPG received from connection manager according to user preference. Is also classifies the interactivity traffic and forwards it to the proper entities.

C. Resource Manager

The resource manager Interacts with the WiMAX stack and performs the local optimizations. It receives the use QoS requirements from the Service manager and provisions network resources accordingly. It

February 26, 2010 DRAFT 6 performs local optimizations like congestion control through video adaptation, creating TDD frames for optimal bandwidth utilization, frequency and modulation selection based on channel conditions etc.

V. DESIGN ALTERNATIVES

We consider four design alternatives for our testbed. First, we consider a totally software based simulation of WiMAX network. This design is very cost effective and can provide high flexibility. However, simulation software often abstract many details of a real hardware and hence may not adequately represent the real network. The second alternative is to use a mix of simulation and hardware tools. In this the simulator provides the necessary customization facilities while the associated hardware ensures representation of real life scenario. The third alternative we consider is a proof of concept testbed where only the basic hardware components like baseband and RF chips are procured and they are interfaced together at the lab. The advantage of this system is lower cost and highly flexible customization options. On the down side, we need to spend lot of time in integrating the components and fine tuning the hardware for our requires functionality. In the fourth design, off-the-shelf hardware and software solutions are procured and then customizations are built on top the system. This system will offer more reliability and represent the real life system in a closer way but will be costlier. Also this design restricts changes in the software to very few predefined customizations which might not be very useful for research purposes. We note that we still have to implement the SM and CM modules for the off-the-shelf design. In the rest of this section we describe the different design alternatives in more detail.

A. Pure Simulation based Design

In this design the entire testbed is based on some software simulation of a WiMAX network. WiMAX modules for the popular network simulators like OPNET, NS and OMNET are available. In Table I we compare the three prominent simulation platforms available for WiMAX.

B. System-in-the-Loop Design

System-in-the-loop is a concept in which a simulator interacts with the real environment. Such a facility provided by the OPNET simulator [11] through its SITL module. However, the module currently interacts only through Ethernet connection.

C. Proof-of-Concept Design

A proof of concept design using basic hardware components like baseband, RF circuitry and antenna is a cost effective and fast option for developing a testbed. However this comes at the cost of high

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TABLE I: List of WiMAX simulators Name Description OPNET [7] OPNET is a well established commercial grade network simulator which has been devel- oping modules to support WiMAX related features and entities in its network modelling environment. In release 14.5 WiMAX base station and subscriber stations were included with mobility support. The models are claimed to be IEEE 802.15e compliant and includes advanced features like ... The models however do not support Multicast services and the power saving mechanisms are not implemented. Pros: Commercial grade reliability and high acceptance. Cons: High cost and stiff learning curve. Less extendability. NS-3 [8] NS-3 is a successor of the well known NS-2 network simulator. Although NS-3 simulator is not in widespread use yet, the rigorously implemented WiMAX module has already received attention of the academic community. However the module still lacks many basic features like packet fragmentation support. It does not support the multicast broadcast support or sleep mode options. Pros: open-source, high customization possibilities. Cons: Lacks support for many features. Not in widespread use. Omnet++ [9] A project has been recently completed that implements a WiMAX module over the opmet++ network simulation platform. The project focuses on mobility and IPv6 support in WiMAX networks and does not provide a full implementation of the standard. Pros: open-source, good implementation of the mobility module. Cons: Not a full implementation of the standard. Not in widespread use. matlab [10] there is matlab module available for the WiMAX OFDMA PHY and a second module for the MAC is being developed. However these modules can only used for theoretical verification of frame construction as they cannot represent network configuration.

complexity of assembling the hardware and significant software implementation effort. We consider a configuration where the subscriber devices are procured from market, the ASN-GW is implemented in a desktop computer and only the base station is assembled from scratch. The three major components of the base station are the baseband module, the radio frequency module and the antenna. Antenna is usually available as a commodity item. So we focus on the other two components. The hardware is generally implemented in either a SoC form or a ASIC form. The main difference between SoC and ASIC design is that in SoC a different number of ASIC components are integrated into a single chip and usually the lower layer of software stack is also bundled with the hardware. This results in a more robust hardware performance and less development effort for the testbed. Another option is FPGA based

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(a) (b)

Fig. 4: SoC and ASIC reference designs for WiMAX base station

WiMAX boards which provide fast prototyping of ASIC or SoC design at the cost of slightly degraded hardware performance. In Figure 4 the difference between SoC and ASIC reference designs is captured. In Table II we list a few available products for the three design options.

D. Off-the-Shelf Design

In off-the-shelf design WiMAX base station, subscriber and ASN-GW hardware are procured form hardware vendors and only the application layer is built on top of it. This provides near-commercial grade representation of WiMAX networks. However this setup has two major drawbacks. The first is that the hardware vendors generally provide proprietary binary code for their hardware thus making fine grained customization very difficult. The second deterrent is the prohibitively high cost of these hardware, particularly for small scale deployments. There have been some open source initiatives for building a WiMAX stack for the subscriber devices but so far no such attempts have made for a base station stack. In Table III we describe some open source projects for redeveloping WiMAX subscriber station stack.

VI. IMPLEMENTATION ISSUES

WiMAX spectrum is fragmented into many bands and different countries have regulated different bands are licenced or licence free. In Canada, the only licence-exempt band for WiMAX is the 5.8GHz band [15]. Therefore this should be consideration while procuring base station hardware. Normally a WiMAX base station serves thousands of users over a wide area. These full scale base stations, also known as macro base stations, are very costly and incur high operational cost. Therefore for a lab setup we only consider the shorter range base stations, the micro and pico base stations.

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TABLE II: List of SoC, ASIC or FPGA solutions SoC/ASIC Solutions SEQUANS (web) Mobile WiMAX Compliant. Reference USB -NA- SQN1130 (MS) and Dongle available From Quanta SQN2130 (BS) Wavesat (web) Subscriber side SoC based implementation of -NA- Odyssey 8500 the 802.16e standard. Development Kit in- cludes reference designs in USB and other form factors DesignArt (web) Open SoC Platform $40,000 DAN2400-RD BTS SoC picoChip (web) C8350 Mobile WiMAX compliant -NA- SoC FPGA Solutions Altera(web) Stratix II platform -NA- Xillinx(web) Virtex6 FPGA solution. Xillinx FPGA boards -NA- are used by Wavesat for their SoC prototype development Sundance(web) C6455 FPGA Solution board with USB inter- $16,000 face

A. Open Source Software

Currently no open source WiMAX implementations are known for the base station. Following are some open-source initiatives relevant to our testbed. 1) openIMS: Since WiMAX provides an all IP interface the service manager platform can be built using IMS. Open source implementations like openIMS [16] can be used for this purpose. We still need to develop the portions specific to WiMAX service provisioning. The resource manager basically has to be the WiMAX stack implementation at the base stations. There exist open source media steaming applications like the UCT IMS Client [17] which support video streaming over IMS. Currently work is underway for a IPTV over IMS in the same project. This can be used as a starting point for the WiMAX specific solution. 2) wireshark: Recently WiMAX support was added to the well known packet analysis tool Wire- shark [18]. This might be helpful in analyzing the MAC packets through a Subscriber device interface.

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TABLE III: List of Open Source WiMAX Subscriber Stacks Name Description linuxwimax [12] linuxwimax is an Intel initiated project containing an open source WiMAX stack for the Intel 5x50 series of WiMAX hardware. It implements the mobile WiMAX 802.16e standard and provides API for application development. The code base is separated into kernel space and user space services and provides a device agnostic hardware interface. Some of the code is still in binary form which are planned to be made open at a later point. madwimax [13] madwimax is a Linux driver which works for the Samsung based WiMAX USB devices. The project started by reverse engineering the Samsung drivers meant for use in Yota’s WiMAX network in Russia. However, it does not contain a WiMAX stack API for development. boc-wimax [14] boc-wimax is a WiMAX stack developed by Bellore Telecom of France for their Maki WiMAX CPE device. The open source code is claimed to work with the SEQUANS chips. They also include a skeleton implementation of the base station and ASN gateway. In their skeleton implementation the ASN-GW uses EAP for implementing security and DHCP for user provisioning. When the subscriber stack is run on the Maki device it communicates to the base station via Maki’s WiMAX interface. Otherwise the subscriber tries to connect to the base station over Ethernet.

B. Estimated Cost

Due to the recent deployments a lot of vendors have come up with their WiMAX products. For a black box design we have to look into two kinds of hardware. The WiMAX base station and the stationary or mobile subscriber station. First we look at the main Canadian vendors offering WiMAX equipment. In Canada the WiMAX is still used for mostly fixed broadband data services and hence 802.16d is the prevalent standard. In Table IV we list the Canadian vendors, their products and an estimated cost. We observe that almost all the vendors offer only 802.16d products and they also have they proprietary CPE. Therefore a starting setup can be obtained for a price range of $18000-$20000. However these setups neither support mobile subscribers nor do they have multicast/broadcast capability. This severely limits the range of research possibilities. We note that SR Telecom and more recently Readline has introduced products which can be optionally evolved into mobile WiMAX via software upgrades. However these products are costlier than those mentioned here and also in early stage of development. On another note, Tranzeo offers a reasonable start-up package at a very attractive price. We next look at the international suppliers for base station vendors and list some of them in Table

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TABLE IV: List of WiMAX manufacturers in Canada Name Product Description Price Tranzeo Wire- TR-WMX 5.8 802.16d compatible pico base station $1600-$2200 includes one base less (web) GHz Kit operating on 3.6 or 5.8 GHz bands, station , 2 CPE and cables does not have any specification details regarding download speed, subscriber capacity etc. Vecima VistaMAX 802.16d compatible macro base station $5000 includes one 120 sector Networks 3.65 GHz Kit operating on 3.65GHz band, maximum base station , 5 CPE and cables (web) usable downlink speed is 22Mbps at 64 QAM modulation. RedLine Com- RedMAX AN- 802.16d compatible macro base station $6875 for the base station munications 100U operating on 3.6GHz band, maximum alone. does not include an- (web) usable downlink speed is 23Mbps and tenna, NMS, cabling or sub- NLOS range is 3km scriber units SR Telecom symmetryMX 802.16d or 802.16e compatible macro - (web) and base station operating on 10 GHz band. symmetryMXe Base station software includes service flow manager and supports MCBCS DragonWave - WiMAX based back haul solutions - (web) EION wireless Libra MAX-LT 802.16d compatible macro base station $5000 for the base station (web) 5800 operating on 5.8 GHz band, effective bandwidth of 20Mbps on a 10MHz operation

V. While Motorola and Alvarion have comprehensive solutions they are significantly more expensive. In fact Alvarion has a multimedia focused solution, described as 4motion in their website, which claims full implementation of multimedia service layer using MCBCS. Airspan’s MicroWiMAX solution looks like good value for the money, as it can be software upgraded to mobile WiMAX. Next we look into the subscriber station equipments. Most of the base station vendors have their own subscriber station devices. Here we look at some different devices which are available as retail consumer goods. We can broadly classify the available gadgets into two categories. First are the handheld devices which are solely meant for the mobile WiMAX. As of now there are only few handheld devices available with WiMAX capability. We list them in Table VI. We note that all these devices are custom made for

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TABLE V: List of Base Station solutions Vendor Product Description Price Proxim (web) Tsunami MP.11 802.16d compatible macro base station $7000 operating on multiple free bands in- cluding 5.6GHz band. Uses proprietary WORP protocol in frequency bands of 5MHz. 6-50Mbps download speed over a 2-20 miles coverage area. Motorola (web) WAP 400 802.16e compatible macro base station $14000 working on 3.6GHz band with IMS based service layer software. Alvarion (web) BreezeMAX 802.16e compatible macro base station $9000 Extreme 5000 operating on 5.6GHz band. Can sup- port up to 512 subscribers. Airspan (web) MicroMAX 802.16d compatible micro cell base $1800 station operating on 5.8GHz band. Software upgradable to mobile WiMAX

TABLE VI: List of Handheld solutions Vendor Product Description Price HTC MAX 4G Smartphone with Dual operation of $1200 (web) GSM and WiMAX Samsung SPH-M8200 WiBro and CDMA dual phone $500 (web) Samsung Mondi Internet Tablet $500 (web) Nokia N810 WiMAX Internet Tablet $450 (web) edition

different network operators (for example HTC MAX 4G is designed for Yota’s network in Russia), and might not be available in the open market. The other type of devices are USB dongles or PCI/Express cards for laptops or mobile phone. Leading Laptop OEMs have started bundling dual WiFi/WiMAX cards in their laptop models. Already several models are available from vendors like DELL,Lenovo,Asus and Samsung. These devices mainly have stationary/nomadic features but many of them support full mobility as well. We present a cost estimate of the SoC based testbed in Table VII and that of an off the shelf testbed

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TABLE VII: Approximate Cost of a SoC based testbed Vendor Product Description Price SUNDANCE FPGA board WiMAX Platform Reference Kit $16000 Mobile Mark ECO6-3500 3.5GHz Omnidirectional BS antenna with 6dB gain $100 ZyXEL MAX 100 Moblie WiMAX PCI Card with SEQUANS Chip $90 Intel 5150 Wireless Card Dual WiFi/WiMAX card $60 HTC MAX 4G Dual GSM/WiMAX Unlocked phone &1200 Total (USD) $18,000

TABLE VIII: Approximate Cost of a Off-the-shelf testbed Vendor Product Description Price IPAXIOM 802.16e Base station Mobile WiMAX Compliant base station $7000 ZyXEL MAX 100 Moblie WiMAX PCI Card with SEQUANS Chip $90 Intel 5150 Wireless Card Dual WiFi/WiMAX card $60 HTC MAX 4G Dual GSM/WiMAX Unlocked phone &1200 Total (USD) $9,000

in Table VIII.

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REFERENCES

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