Performance of MIMO with Frequency Domain Packet Scheduling in UTRAN LTE Downlink

Abstract

This paper addresses the performance of spatial division multiplexing (SDM) multiple-input multiple-output (MIMO) techniques together with frequency domain packet scheduling (FDPS) based on UTRAN Long Term Evolution (LTE) downlink. Two SDM concepts currently considered in 3GPP are the single-user (SU-) and the multi-user (MU-) MIMO. For MU-MIMO, multiple users can be scheduled on different streams on the same time-frequency resource, while SU-MIMO restricts one time-frequency resource to a single user. Both concepts are analyzed against the 1x2 maximal ratio combining (MRC) case, using the proportional fair (PF) criterion extended to frequency and spatial domains. The realistic finite buffer best effort traffic model is used in the study. Results show that in the macrocell scenario, the combination of FDPS and SDM (SDM-FDPS)without precoding achieves only marginal gain in cell throughput, due to limited SINR dynamic range. The gain is increased to around 20% when precoding is applied. In the micro-cell scenario, the gain of SDM-FDPS over the reference scheme is increased up to 35% with precoding.

Comparative Performance Study of LTE Downlink Schedulers

“…A study of the PF scheduler performance applied to a video streaming in HSDPA-based cellular system can be found in [19]. The PF scheduler is commonly used as a reference scheduler for the experiments performed among others in [13] and [21].…”

Analysis of Channel Capacity for LTE Downlink Multiuser MIMO Systems

“…Denote by ζ k the set of users scheduled on the k th PRB and |ζ k | = n t . Without precoding, the received signal vector at the jth MS, j ∈ ζ n , can be modeled as y n,j = H n,j x n + n n,j , where n n,j ∈ C nr×1 is a circularly symmetric complex Gaussian noise 2 In the localized FDMA transmission scheme, each user's data is transmitted by consecutive subcarriers, while for the distributed FDMA transmission scheme, the user's data is transmitted by distributed subcarriers [1]. 1 vector with a zero mean and covariance matrix N 0 I ∈ R nr×nr , i.e., n n,j ∼ CN (0, N 0 I); H n,j ∈ C nr×nt is the channel matrix between the BS and the jth MS at the nth PRB and x n ∈ C nt×1 is the transmitted signal vector at the nth PRB, and the µth element of x n is the data symbol x n,µ transmitted from the µth MS, µ ∈ ζ n .…”

SINR distribution for LTE downlink multiuser MIMO systems

“…With the localized transmission 1 Open loop and closed loop MIMO correspond to the MIMO systems without and with channel state information at the transmitter, respectively [1]. 2 In the localized FDMA transmission scheme, each user's data is transmitted by consecutive subcarriers, while for the distributed FDMA transmission scheme, the user's data is transmitted by distributed subcarriers [1].…”

“…SDM is used to improve the spectral efficiency of the system, while FDPS allows the packet scheduler at the Base Station (BS) to exploit the available multiuser diversity in both time and frequency domain. In [2], it is shown that the MIMO schemes with combined SDM and FDPS can further enhance the system performance.…”

“…However, the use of closed loop provides both diversity and array gains, and hence a superior performance. Due to its simplicity and robust performance, the use of linear precoding has been widely studied as a closed loop scheme [2]. Here, we refer to the open loop MIMO as the SDM MIMO without precoding, and the closed loop MIMO as the linearly precoded SDM MIMO.…”