Interference Rejection Combining in LTE Networks

Abstract

Long Term Evolution (LTE) provides high spectral efficiency within one cell, but it is shown to be highly vulnerable to inter‐cell interference. While LTE as well as Wideband Code Division Multiple Access (WCDMA) suffers uplink interference especially with a frequency reuse factor of one, WCDMA has some inherent layer 1 mechanisms to alleviate these effects, namely macro‐diversity and spreading codes. In contrast, LTE user data are more localized in the time/frequency domain, calling for different mechanisms for interference reduction in the receiver. For the higher layers, techniques such as fractional power control or fractional frequency reuse can be used to mitigate the interference but are shown to be sub‐optimal. For layer 1, interference rejection combining (IRC) is described as an efficient alternative to increase uplink bit rates in areas where cells overlap. IRC principles in the presence of radio fading channels are detailed, while strategies for both interference suppression and signal‐to‐interference‐plus‐noise ratio (SINR) maximization are considered. Taking a didactic approach, we compare multiple antenna receiver techniques (maximal ratio combining (MRC), IRC, multiple input multiple output (MIMO)), analyze the key factors of IRC efficiency (the number of receiving antennas and interferers, time synchronization, interference over thermal, and scheduling decisions), and provide link level performance comparisons. We also provide implementation considerations for integrating the IRC in the current eNodeB receiver. As the purpose of this paper is to give a basic level introduction to IRC applied to the LTE uplink and highlight the respective surroundings, the IRC approach will be covered rather intuitively by illustrations without a great deal of theoretical detail. © 2012 Alcatel‐Lucent.

Effects of Interference Mitigation and Scheduling on Dense Small Cell Networks

“…However, the presented gains are so significant that there could be an overall throughput improvement even when taking into account the associated loss from muting. Another possibility is to let the user equipments suppress part of the interference by means of advanced receivers [7], [16] with interference cancellation capabilities, either in a linear or non-linear way. Future work should consider applying the findings presented in this paper to the design of joint inter-cell interference mitigation techniques combining some of these options.…”

Experimental performance evaluations of CoMP and CA in centralized radio access networks

“…3GPP technical report 36.819 is providing LTE physical layer aspects in Release 11 [14]. Interference rejection algorithms such as interference-rejection combining [15] have enabled the possibility of usage of multiple cell antennas for UL CoMP. CoMP which is released as LTE-A feature is expected to be an advanced for 5G New Radio (NR) as well [16].…”

“…Interference mitigation gains are obtained for cell-center UEs that experience interference due to intra-frequency neighbor cell from UL CoMP CEUs. Together with joint interference rejection algorithms [15], cell-center UE's interference can be mitigated. The interference mitigation gain is proportional to the original interference received from UL CoMP CEUs.…”

Efficient co-channel interference suppression in MIMO-OFDM systems

“…In the meanwhile, universal frequency reuse is employed in these systems to support more users with higher data rates. As a result, the inevitable co-channel interference (CCI) has become the limiting factor that dominates the system performances [3][4][5][6].…”

“…Interference rejection combining (IRC) is an efficient CCI suppression technique employed at the receiver side [3][4][5][6]. It can be based on minimum mean square error (MMSE) criterion or maximizing the signal-to-interference-plus-noise ratio (SINR) criterion.…”