Efficient QoS-based Uplink Scheduling in IEEE 802.16e Mobile Stations The LightB - Sponsored Whitepaper

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High-speed mobile access to Internet services has been driving the cellular industry to look for new technologies beyond 2.5 and 3G, such as, HSPA, EVDO, and LTE. Moreover, while WiFi networks provide the ubiquity and high-date rates, they fail to provide true mobility and extended range. In response, the IEEE 802 group worked on extending the IEEE 802.16-2004 (previously known as 802.16d) [1]. The result was the IEEE 802.16e-2005 standard [2-3] which provides a packet-based non-line-of- sight broadband wireless access. The standard mainly extends the base 802.16-2004 to support mobility and energy-efficient sleep and idle modes suitable for mobile devices operated by energy-limited batteries. Both the 802.16-2004 and 802.16e-2005 standards support multiple advanced features such as orthogonal frequency division multiple access (OFDMA), multi-input multi-output MIMO with space-time coding and spatial multiplexing options, beam forming and adaptive antenna system (AAS), adaptive modulation and coding (AMC), time-division duplexing and frequency-division duplexing modes among others. This rich feature set is intended to provide data rates in excess of tens of megabits per second. As such, WiMAX should meet mobile Internet access requirements. It supports multiple handoff mechanisms, ranging from hard handoffs to soft handoffs, power-saving mechanisms for mobile devices, and advanced quality-of-servce (QoS) and low latency for improved support of real-time applications with an optimized service class particularly for VoIP. The IEEE 802.16e standard is complimented by interoperability and conformance specifications defined by the WiMAX Forum [4-6]. The commercial realizations of products based on the 802.16e standard are typically

referred to as mobile WiMAX (same as IEEE 802.11 products are commercially known by the name WiFi). There are a few crucial factors that give WiMAX an edge over other competing wireless technologies, which include [7]: 1. Superior radio performance: this is largely tied to the use of OFDMA, a multiplexing technique well suited to multipath environments that gives network operators higher throughput and capacity, great flexibility in managing spectrum resources, and improved indoor coverage. In addition, support of various MIMO modes, beam forming, and hybrid ARQ also boost throughput the efficiency of the radio link. 2. Spectrum usage: Mobile WiMAX can be deployed in several licensed bands (2.3 GHz, 2.5 GHz, 3.3 GHz, 3.4-3.8 GHz) with channel sizes ranging from 3.5 MHz to 10 MHz. The availability of multiple FFT sizes fit different channel bandwidth. This gives operators the flexibility to use WiMAX in multiple spectral bands in the available spectrum they have. 3. Advanced IP-based architecture: Mobile WiMAX is based on IP-core and its protocol model is designed with a packet-transport model. Therefore, it should enable the transition to an all-IP network. In essence, the WiMAX Forum is working on supporting IP MultiMedia Subsystem (IMS) and its 3GPP2 counterpart, MultiMedia Domain (MMD). 4. Native protocol support of multiple services: Mobile WiMAX supports five classes of service that could serve multiple applications including circuit-like operations, VoIP, video streaming, and web traffic. The medium access control (MAC) layer also encapsulates functionality for traffic policing for enabling user-network traffic contracting and control. The following section provides details about the WiMAX QoS model. In this paper, we focus on one of the important aspects of mobile WiMAX, namely the scheduling performance at the mobile stations. We consider the scheduling problem from two aspects. The first is satisfying the functional requirement in, sharing the allocated BW resource between different connections according to negotiated QoS parameters of each connection. The second is to introduce a computationally efficient algorithm to meet the real time constraints on typical mobile hardware platforms. The rest of this paper is organized as follows. In section 2, we provide a brief overview of the quality of service model in WiMAX. Section 3 gives details about the proposed uplink scheduling. The corresponding results showing its excellent performance are presented in section 4. Details of the implementation on an ARM9 processor core, and real-time performance are provided in section 5.

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2. WiMAX Quality-of-Service Model WiMAX layer 2 transport is a connection-oriented protocol. All data transports must be established in advance between the base station and mobile station. The service is based on a centralized media access and resource management scheme where all resources are centrally managed by the BS. The BS has complete information about the attached MS's and their established connections. The uplink medium access is based on a request/grant mechanism, where the mobile station (MS) requests bandwidth from ...
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