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Mobile Station (mobile + station)

Distribution by Scientific Domains

Engineering	80%

Selected Abstracts

Resource allocation algorithms for minimum rates scheduling in MIMO-OFDM systems,

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2010
Johannes Georg Klotz
In this paper, we consider a multiple-input-multiple-output-orthogonal frequency division multiplexing (MIMO-OFDM) downlink scenario, where each receiving mobile station has quality of service requirements, namely minimum rate requirements. For this problem we propose three heuristic resource allocation algorithms, which have a much lower complexity than the existing optimal solution (opt). We compare and evaluate these algorithms according to sum rate performance and complexity. The first strategy is based on a heuristic sum rate maximisation algorithm using the so-called eigenvalue updates. In our second algorithm, we make use of the duality of uplink and downlink, which allows us to do the allocation in the dual uplink. Finally, our third algorithm is based on the well-known zero-forcing dirty paper coding (ZF-DPC) principles, which use the Gram--Schmidt process to orthogonalise the transmissions towards the different users. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Joint packet scheduling and dynamic base station assignment for CDMA data networks

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2008
Christian Makaya
Abstract In current code division multiple access (CDMA) based wireless systems, a base station (BS) schedules packets independently of its neighbours, which may lead to resource wastage and the degradation of the system's performance. In wireless networks, in order to achieve an efficient packet scheduling, there are two conflicting performance metrics that have to be optimized: throughput and fairness. Their maximization is a key goal, particularly in next-generation wireless networks. This paper proposes joint packet scheduling and BS assignment schemes for a cluster of interdependent neighbouring BSs in CDMA-based wireless networks, in order to enhance the system performance through dynamic load balancing. The proposed schemes are based on sector subdivision in terms of average required resource per mobile station and utility function approach. The fairness is achieved by minimizing the variance of the delay for the remaining head-of-queue packets. Inter-cell and intra-cell interferences from scheduled packets are also minimized in order to increase the system capacity and performance. The simulation results show that our proposed schemes perform better than existing schemes available in the open literature. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Empirical evaluation of receiver-based TCP delay control in CDMA2000 networks

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2007
Oh-keun Kwon
Abstract Wide-area broadband wireless technologies such as CDMA2000 often suffer from variable transfer rate and long latency. In particular, TCP window-based rate control causes excessive buffering at the base station because of the lower transfer rate of the wireless link than that of the wired backhaul link. This performance characteristic of TCP further increases the end-to-end delay, and additional resources are required at the base station. This paper presents a practical mechanism to control the end-to-end TCP delay for CDMA2000 networks (or other similar wireless technologies). The key idea is to reduce and stabilize RTT (round-trip time) by dynamically controlling the TCP advertised window size, based on a runtime measurement of the wireless channel condition at the mobile station. The proposed system has been implemented by modifying the Linux protocol stack. The experiment results, conducted on a commercial CDMA2000 1x network, show that the proposed scheme greatly reduces the TCP delay in non-congested networks, while not sacrificing the TCP throughput in congested networks. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Carrier-sense-assisted adaptive learning MAC protocols for distributed wireless LANs

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2005
P. Nicopolitidis
Abstract A Carrier-sense-assisted adaptive learning MAC protocol for wireless LANs, capable of operating efficiently in bursty traffic wireless networks with unreliable channel feedback, is introduced. According to the proposed protocol, the mobile station that is granted permission to transmit is selected by means of learning automata. At each station, the learning automaton takes into account the network feedback information in order to update the choice probability of each mobile station. The proposed protocol utilizes carrier sensing in order to reduce the collisions that are caused by different decisions at the various mobile stations due to the unreliable channel feedback. Simulation results show satisfactory performance of the proposed protocol compared to similar MAC protocols. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Evolution of the reverse link of CDMA-based systems to support high-speed data

BELL LABS TECHNICAL JOURNAL, Issue 3 2002
Nandu Gopalakrishnan
Development of an upcoming release of the CDMA2000* family of standards is expected to focus on enhancing the reverse link (RL) operation to support high-speed packet data applications. The challenge is to design a system that yields substantial throughput gain while causing only minimal perturbations to the existing standard. We are proposing a system that evolves features already present in the CDMA2000 Release B and IS-856 (1xEV-DO) standards and reuses concepts and capabilities that have been introduced for high-speed packet data support on the forward link (FL) in Release C of the CDMA2000 standard. The RL of Release C of the CDMA2000 standard supports a relatively slow scheduled operation of this link using signaling messages. Scheduling with shorter latencies can be achieved by moving this functionality to the physical layer. Concurrently, both the FL and RL channel conditions may be tracked, and users may be scheduled based on this knowledge. To further manage the power and bandwidth cost on the FL, that is, of scheduling users' transmissions on the RL, the mobile station (MS) is permitted to operate in either a scheduled mode or an autonomous mode. A capability is provided for the MS station to switch the mode of operation. Performance impact of, and gain from, some of the system features is characterized through simulation results. © 2003 Lucent Technologies Inc. [source]