Cross-Layer-Optimized User Grouping Strategy in Downlink Multiuser MIMO Systems
Cross-Layer-Optimized User Grouping Strategy in Downlink Multiuser MIMO Systems
复制标题
下行多用户 MIMO 系统中跨层优化的用户分组策略
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
M. Takagi
中科院分区：
文献类型：
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作者：
T. Tandai;Hiroki Mori;M. Takagi
针对ieee802.11无线局域网（WLAN）下链路多用户（MU）多输入多输出（MIMO）系统，提出了一种跨层优化的用户选择和分组传输技术。在IEEE 802.11 WLAN中，数据包的持续时间由数据大小和选择的传输模式（调制和编码方案，MCS）决定，因此，通常每个用户的数据包持续时间会根据信道条件和应用而变化。如果选择多个数据包持续时间差异较大的用户作为下行MU-MIMO传输的目标，则会降低空间复用的效率，无法提高网络吞吐量。在选择用户作为下行MU-MIMO传输的目标时，必须考虑用户之间的空间信道相关程度（从物理层的角度）和队列中的数据包等待时间（从MAC层的角度）。除了这些标准之外，在IEEE 802.11 WLAN中，用户之间数据包持续时间的一致性必须被视为一个标准。该方法根据空间兼容性和数据包等待时间选择用户后，调整数据大小，使用户的数据包持续时间统一。这意味着所提出的下行MU- MIMO传输通过跨层方法在三个维度上进行了优化：空间信道相关性，分组等待时间和分组持续时间的均匀性。计算机仿真结果表明了该方法的有效性。
This paper proposes a cross-layer-optimized user selection and packet transmission technique for the downlink multi-user (MU) multiple-input multiple-output (MIMO) system in IEEE 802.11 wireless LAN (WLAN). In IEEE 802.11 WLAN, packet duration is decided by a data size and a selected transmission mode (modulation and coding scheme, MCS), and therefore, in general, the packet duration of each user varies according to the channel conditions and the applications. If multiple users whose packet durations are considerably different are selected as the target of the downlink MU-MIMO transmission, then the efficiency of spatial multiplexing degrades and the network throughput cannot be enhanced. When selecting users as the target of the downlink MU-MIMO transmission, the degree of spatial channel correlation among users (from the viewpoint of the physical layer) and the packet waiting times in a queue (from the viewpoint of the MAC layer) have to be considered. In addition to these criteria, in IEEE 802.11 WLAN, uniformity of the packet durations among users has to be considered as a criterion. In the proposed method, data size is adjusted in order to make the packet durations of the users uniform after selecting the users based on the spatial compatibility and the packet waiting times. This means that the proposed downlink MU- MIMO transmission is optimized in 3 dimensions by the cross- layer approach: the spatial channel correlations, packet waiting times and the uniformity of the packet durations. Computer simulations are performed and the results show the effectiveness of the proposed method.