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In this paper, we propose and give the performance of a novel uplink system based on the combination of multi-carrier (MC), code division multiple access (CDMA) and multiple input multiple output (MIMO) techniques. We focus on the SS-MC-MA scheme, where each user spreads its data symbols on a specific subset of adjacent or multiplexed subcarriers, to facilitate the channel estimation and reduce complexity...
To satisfy the increasing demand for wireless systems capacity, the industry is dramatically increasing the density of the deployed networks. Like other wireless technologies, Wi-Fi is following this trend, particularly because of its increasing popularity. In parallel, Wi-Fi is being deployed for new use cases that are atypically far from the context of its first introduction as an Ethernet network...
In this paper, after discussing the challenges raised by the increasing density of IEEE 802.11 WLANs, we investigate a new combination of transmit power control and physical carrier sensing adaptation to leverage the spatial reuse in high density deployments. While each of these techniques when applied separately is efficient in enhancing the performance of such dense scenarios, they suffer from serious...
Recently, the High Efficiency WLAN or simply HEW study group was created within IEEE 802.11 working group. This study group considers the improvement of spectrum efficiency to enhance the system's area throughput in high density scenarios. Subsequently, this led to the creation of a new task group called 802.11ax, which is expected to deliver the next Wi-Fi generation. A key perspective considered...
The rate control mechanism is an effective way to improve the overall system performance in IEEE 802.11 multi-rate networks. However, in dense environments, due to the large number of contending nodes, the packet collisions trigger unfairly the rate control mechanism to decrease the transmission data rate. In this work, we address the performance degradation problem of rate control caused by these...
In future's high density Wireless Local Area Networks (WLANs), to improve the overall throughput, we envision the optimization of the MAC protocols and mechanisms. Traditionally, it's clear in the literature that Transmit Power Control (TPC) is chosen as one of the most powerful tools for optimizing MAC protocols. However, the TPC is not always possible to implement due to hardware and licensing limitations...
In this paper we propose an efficient way to transmit accurate channel estimation to the transmitter when this latter requires them in order to calculate its precoding vectors. Since number of channel coefficients that need to be sent back to the transmitter, especially when the number of transmit and receive antennas as well as the number of subcarriers of OFDM systems increase, studies on limited...
This paper deals with a novel low complexity implementation of the DCT based pilots channel estimation for WLAN system. After the description of the existing DCT based method, a new implementation design named Modified Lee algorithm is proposed. The complexity is reduced by 30% compared to the Lee algorithm. Finally this new design is synthesized for a FPGA component and its efficiency is validated...
In this paper, we address the problem of scheduling a LDPC coded iterative MIMO OFDM receiver. Iterative reception is an efficient way to approach optimal performance avoiding exhaustive algorithms. In such receivers using LDPC codes, complexity and delay could be critical since decoding and equalization tasks are repeated at each equalization loop. A LDPC decoder stops once it reaches a maximum number...
In this paper we consider channel estimation for MIMO-OFDM systems, specifically when null carriers are placed at the border of the spectrum in order to limit interference with neighboring spectrums. Indeed, the presence of these null carriers leads to degradation on the transform domain channel estimation (TD-CE) because of a "border effect" phenomenon. Truncated singular value decomposition...
In this paper, we investigate the robustness of the spread spectrum multi-carrier multiple access (SS-MC-MA) technique in uplink multicellular systems. In a first step, a statistical characterization of the intercell interference is carried on to model it for BER performance simulations. Then, the impact of the intercell interference on such a scheme is evaluated and the robustness of SS-MC-MA system...
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