Jeremy Gosteau

The evolution of 5GHz WLAN toward higher throughputs

A standardization effort has started within the IEEE 802.11 working group to define the next generation of 802.11 wireless LANs. This article illustrates how throughput achieved above the MAC layer of 5 GHz WLANs can be increased from an existing 30 Mb/s maximum with 802.11a/g to rates exceeding 90 Mb/s. After a brief review of ongoing WLAN standardization activities, the support of a higher physical-layer bit rate by various standardized MAC protocols (802.11, 802.11e, and HIPERLAN/2) is discussed, showing the PHY and MAC layers must be considered jointly in order to achieve a significant throughput increase. Various physical layer techniques are compared in terms of performance and complexity. In particular, simulations show that by relying on MAC layers with good efficiency like 802.11e and HIPERLAN/2, a combination of space-time block coding with a possibility of channel bundling could bring a peak throughput increase from 30 to 90 Mb/s as well as a significant cell range increase.

Analytical developments on QoS enhancements provided by IEEE 802.11 EDCA

This paper quantifies the gain in throughput and quality of service (QoS) provided by the EDCA MAC adopted in the current IEEE 802.11e WLAN draft compared to the traditional DCF. In that purpose, an analytical model is developed to compute the throughput in the single and multi-user cases with a non-ideal channel. This model is hacked with system simulations in realistic deployment scenarios. Results make a clear statement on the advantage of EDCA to guarantee some QoS. Final discussions provide inputs to further improve both the delivered QoS per user and the overall cell throughput for next generation of wireless LANs.

Evaluation of interoperability mechanisms for coexisting HSDPA and WLAN enhanced with MTMR techniques

Concept for 4G systems can be seen as the seamless inter-working between existing and 3G radio networks providing the user with a wide variety of services, while maintaining a large area of coverage and minimum user QoS requirements. This paper investigates interoperability between HSDPA and WLAN systems by proposing some pertinent criteria issued from cost functions for both initial user assignment and inter-system handover. Performance characterization is assessed through scenarios using a simulation platform enhanced with multiple transmit and multiple receive (MTMR) techniques.

Evaluation of Interoperability Criteria and Mechanisms for Seamless Inter-Working Between UMTS-HSDPA and WLAN Networks Enhanced with MIMO Techniques

This article proposes criteria and mechanisms that achieve seamless inter-working between the multi-radio access technologies that will compose the fourth-generation (4G) wireless mobile environment. We address the problem of incorporating system interoperability in order to provide the user with seamless mobility across different radio access technologies; namely we focus on inter-working UMTS-High Speed Downlink Packet Access (HSDPA) and WLAN networks, as these two networks are believed to be major components of the 4G wireless network. Interoperability results in providing the user with a rich range of services across a wide range of propagation environment and mobility conditions, using a single terminal. Specifically, the article aims at defining the criteria and mechanisms for interoperability between the two networks. Our approach considers the use of Cost functions to monitor the essential parameters at the system level in order to trigger an interoperability procedure. Initial user assignment and inter-system handover are considered the incidents that initiate the interoperability algorithm execution. The overall objective of this work is to assess the performance of our developed interoperability platform and to optimize system performance by guarantying a minimum QoS requirement and maximizing network capacity.

Impact of SR-ARQ with Finite Buffer on TDD/TDMA Wireless LAN

In this paper, the influence of some implementation parameters of Selective Repeat Automatic Repeat Request (SR-ARQ) on system performance is investigated. In the framework of the specific SR-ARQ algorithm specified by the ETSI BRAN HIPERLAN/2 (H/2) Wireless LAN standard, the need for optimizing the ARQ signalling bandwidth is illustrated and several signalling strategies are presented. Even with optimum management of the signalling bandwidth, the finite transmit and receive buffers can seriously limit the throughput. This effect is modeled by using a simple probabilistic approach, relying on the TDD/TDMA access scheme, and is evaluated by simulation. The interaction of SR-ARQ with scheduling and Link Adaptation is also discussed and finally, an ARQ aware scheduling strategy is proposed.

Interoperability Criteria and Mechanisms for Seamless Inter-working between UMTS-HSDPA and HIPERLAN/2 Networks Enhanced with MIMO Techniques

The concept 4G wireless communication systems is to provide a user with a rich range of services across different radio access technologies, while maintaining the service’s minimum QoS requirement, independently on the coverage area, mobility conditions, and using a single mobile terminal. To achieve this goal the need for interoperable heterogeneous wireless networks emerges. In this article we identify the challenges that arise when enhancing interoperability functionality to two different radio access networks. Specifically we will focus on inter-working UTRA FDD HSDPA and WLANs networks, as two strong candidates for composing the 4G environment. We also propose an interoperable architecture to achieve seamless inter-working between the aforementioned networks. The article also introduces two interoperable criteria that triggers interoperability based on the use of Cost functions. Namely, these triggers are the initial user assignment to the optimal network and inter-system handover. Each of the two triggers initiates a respective interoperability algorithm. Finally, In order to characterize the interoperability mechanisms behaviour and address an accurate QoS performance analysis, a software simulation platform has been developed. The platform is enhanced with MIMO transceivers and takes into consideration: network configuration, propagation conditions, fast fading, and service requirements.