Macrodiversity

Abstract: Recently, the remarkable capacity potential of multiple-input multiple-output (MIMO) wireless communication systems was unveiled. The predicted enormous capacity gain of MIMO is nonetheless significantly limited by cochannel interference (CCI) in realistic cellular environments. The previously proposed advanced receiver technique improves the system performance at the cost of increased receiver complexity, and the achieved system capacity is still significantly away from the interference-free capacity upper bound, especially in environments with strong CCI. In this paper, base station cooperative processing is explored to address the CCI mitigation problem in downlink multicell multiuser MIMO networks, and is shown to dramatically increase the capacity with strong CCI. Both information-theoretic dirty paper coding approach and several more practical joint transmission schemes are studied with pooled and practical per-base power constraints, respectively. Besides the CCI mitigation potential, other advantages of cooperative processing including the power gain, channel rank/conditioning advantage, and macrodiversity protection are also addressed. The potential of our proposed joint transmission schemes is verified with both heuristic and realistic cellular MIMO settings.

Abstract: Based on random network (RN) topologies generated from Poisson point processes (PPP), this paper investigates the performance of macrodiversity coordinated multipoint transmission (MD-CoMP) in dense cellular networks. First, the signal-to-interference-plus-noise ratio (SINR) outage probability is analyzed for a typical mobile station (MS) and for the global network. Next, a user-centric adaptive clustering method is described, which is designed to maximize each MS's normalized outage capacity (goodput). Simulation are carried out and show that MD-CoMP could significantly improve both the RN and regular hexagonal network (HN) coverage performance by increasing the tenth percentile of the SINR by 12 dB if each MS uses a CoMP cluster of size four. It is also shown that MD-CoMP is more beneficial for the RN since 78 MSs in the RN would choose CoMP to optimize their normalized goodput, whereas this number is 58 in the HN. Moreover, 58 MSs in the RN have their normalized goodput doubled compared with that with no CoMP, whereas this number is 36 in the HN. The impact of predefined clustering schemes is also evaluated, to show the importance of using a fully adaptive clustering to overcome cluster-edge issues, where the MSs' performance is poor due to the limited choices of BSs.

Abstract: In this letter, the effect of maximal ratio combining (MRC)-based macrodiversity on the reverse-link and forward-link capacity in code division multiple access (CDMA)-distributed antenna systems is analyzed. The concept of virtual cell is illustrated, and the analytical outage probability expressions are derived. The present investigation shows that on the reverse link, the interference can be suppressed greatly with macrodiversity, which leads to a significant increase in capacity. However, on the forward-link, it is proven that if simulcasting is used in CDMA-distributed antenna systems, the forward-link capacity cannot increase with macrodiversity whatever power allocation scheme is adopted. Based on the analysis of the cause of capacity loss, a new transmission scheme is further presented and the optimal power allocation scheme is derived. It is shown that, in this case, the forward-link capacity increases rapidly with the number of involved distributed antennas.

Abstract: Millimeter Wave (mmWave) communication systems can provide high data rates, but the system performance may degrade significantly due to interruptions by mobile blockers such as humans or vehicles. A high frequency of interruptions and lengthy blockage durations will degrade the quality of the user's experience. A promising solution is to employ the macrodiversity of Base Stations (BSs), where the User Equipment (UE) can handover to other available BSs if the current serving BS gets blocked. However, an analytical model to evaluate the system performance of dynamic blockage events in this setting is unknown. In this paper, we develop a Line of Sight (LOS) dynamic blockage model and evaluate the probability, duration, and frequency of blockage events considering all the links to the UE which are not blocked by buildings or the user's own body. For a dense urban area, we also analyze the impact of non-LOS (NLOS) links on blockage events. Our results indicate that the minimum density of BS required to satisfy the Quality of Service (QoS) requirements of Ultra Reliable Low Latency Communication (URLLC) applications will be driven mainly by blockage and latency constraints, rather than coverage or capacity requirements.