[show abstract][hide abstract] ABSTRACT: A novel, practical and low-complexity multi-cell OFDMA downlink channel assignment method using a graph- based approach is proposed in this work. The inter-cell interference (ICI) information is obtained through inference from the diversity set of mobile stations (MSs) and presented in the form of an interference graph. The proposed downlink channel assignment method consists of two phases. The task of ICI reduction is mapped to the MAX fe-CUT problem in graph theory and solved in the first phase. Then, channel assignment is conducted by taking into account instantaneous channel conditions in the second phase. State-of-the-art ICI management techniques such as ICI coordination (ICIC) and base station cooperation (BSC) are incorporated in our framework. Heuristic algorithms are proposed to solve both phases of the problem efficiently. Simulation is conducted to demonstrate the effectiveness of the proposed solution, where the SINR improvement can be as high as 4.5 dB. The proposed solution can be used in next generation cellular systems such as 3 GPP long term evolution (LTE) and IEEE 802.16 m.
Global Telecommunications Conference, 2008. IEEE GLOBECOM 2008. IEEE; 01/2009
[show abstract][hide abstract] ABSTRACT: A distributed medium access control (MAC) algorithm for uplink OFDMA networks under the IEEE 802.16 framework is proposed and analyzed in this work. We present a simple yet efficient algorithm to enhance the system throughput by integrating opportunistic medium access and collision resolution through random subchannel backoff. Consequently, the resulting algorithm is called the opportunistic access with random subchannel backoff (OARSB) scheme. OARSB not only achieves distributed coordination among users but also reduces the amount of information exchange between the base station and users. The throughput and delay performance analysis of OARSB is conducted using a Markov chain model. The superior performance of OARSB over an existing scheme is demonstrated by analysis as well as computer simulation.
Global Telecommunications Conference, 2007. GLOBECOM '07. IEEE; 12/2007
[show abstract][hide abstract] ABSTRACT: Performance analysis of multiuser orthogonal frequency division multiplexing (OFDM-TDMA) and orthogonal frequency division multiple access (OFDMA) networks in support of multimedia transmission is conducted in this work. We take a cross-layer approach and analyze several quality-of-service (QoS) measures that incilude the bit rate and the bit error rate (BER) in the physical layer, and packet average throughput/delay and packet maximum delay in the link layer. The authors adopt a cross-layer QoS framework similar to that in IEEE 802.16, where service classification, flow control and opportunistic scheduling with different subcarrier/bit allocation schemes are implemented. In the analysis, the Rayleigh fading channel in the link layer is modeled by a finite-state Markov chain, and the channel state information (CSI) is assumed to be available at the base station. With the M/G/1 queueing model and flow control results, the analysis provides important insights into the performance difference of these two multiaccess systems. The derived analytical results are verified by extensive computer simulation. It is demonstrated by analysis and simulation that OFDMA outperforms OFDM-TDMA in QoS metrics of interest. Thus, OFDMA has higher potential than OFDM-TDMA in supporting multimedia services.
IEEE Journal on Selected Areas in Communications 06/2007; · 3.12 Impact Factor
[show abstract][hide abstract] ABSTRACT: The delay analysis and comparison of OFDM- TDMA and OFDMA using a flow control scheme under the QoS framework of IEEE 802.16 are conducted in this work. We investigate the maximum packet delay performance by deriving delay bounds for several multiaccess modes with different subcarrier/time-slot assignment and bit allocation schemes. The analytical delay bounds provide insights into the performance difference among different multiaccess schemes, and demonstrate each scheme's capability of supporting real-time, delay-sensitive multimedia applications. The derived analytical results are verified by computer simulation.
Global Telecommunications Conference, 2006. GLOBECOM '06. IEEE; 01/2007
[show abstract][hide abstract] ABSTRACT: Performance comparison of multiuser OFDM-TDMA and OFDMA systems by considering physical and link cross-layer behavior is conducted in this work. We provide a new framework for performance evaluation that centers on "scheduling" with several different subcarrier/bit allocation schemes. The performance metrics include: the bit rate, the bit error rate (BER), packet throughput and delay. The instantaneous channel conditions of users are assumed to be available at the base station, which can be achieved by channel estimation at the mobile terminal (MT), and then fed back to the base station through a control channel. To perform the link layer comparison, we model the Rayleigh fading channel with a finite-state Markov chain, and adopt the M/G/1 queueing model as the analytical tool. Computer simulation is performed to verify conducted analytical results.
[show abstract][hide abstract] ABSTRACT: The delay analysis and comparison of OFDM- TDMA and OFDMA using a flow control scheme under the QoS framework of IEEE 802.16 are conducted in this work. We investigate the maximum packet delay performance by de- riving delay bounds for several multiaccess modes with different subcarrier/time-slot assignment and bit allocation schemes. The analytical delay bounds provide insights into the performance difference among different multiaccess schemes, and demonstrate each scheme's capability of supporting real-time, delay-sensitive multimedia applications. The derived analytical results are veri- fied by computer simulation. I. INTRODUCTION Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) are two well-known tech- niques for resource management in multiaccess communica- tion systems. When combined with Orthogonal Frequency Di- vision Multiplexing (OFDM), they are called OFDM-TDMA and OFDMA (OFDM Access), respectively. Both of them have been adopted by the IEEE 802.16 standard as two options for transmissions at the 2-11 GHz band (1). In order to carry multimedia applications, which demand a wide range of quality-of-service (QoS) requirements, the embedment of QoS provisioning in the multiaccess systems is needed. In fact, a QoS framework in the medium access control (MAC) layer has been integrated with the multiaccess transmission systems in the IEEE 802.16 standard (2). In this work, we consider a similar QoS framework under which we compare OFDM- TDMA and OFDMA with various scheduling methods.
Proceedings of the Global Telecommunications Conference, 2006. GLOBECOM '06, San Francisco, CA, USA, 27 November - 1 December 2006; 01/2006