This paper studies the channel asymmetric characteristic between a downlink and an uplink channel in orthogonal frequency division multiple access (OFDMA)/ time division duplexing (TDD) systems. To investigate the downlink and uplink channel asymmetry, we derive a propagation loss mo-del and a shadowing model taking into consideration geometrical information and inter-cell interference. Then, t...

In-band full-duplex (FD) communication is considered a potential candidate to be adopted by the fifth generation (5G) cellular networks. FD communication renders the entire spectrum simultaneously accessible by uplink and downlink, and hence, is optimistically promoted to double the transmission rate. While this is true for a single communication link, cross-mode interference (i.e., interferenc...

We study the effect of fixed clock frequency offsets on the performance of multicarrier direct-sequence CDMA (MCDS-CDMA) for both uplink and downlink communication, assuming orthogonal spreading sequences. We show that for both uplink and downlink MC-DS-CDMA, the performance in the presence of a clock frequency offset rapidly degrades with an increasing number of carriers. It turns out that thi...

In this paper, we study the sensitivity of uplink and downlink MC-DS-CDMA to carrier frequency offsets, assuming orthogonal spreading sequences. For both uplink and downlink MC-DS-CDMA, we show that the performance rapidly degrades for an increasing ratio of maximum frequency offset to carrier spacing. We point out that the degradation in the uplink is larger than in the downlink, because only ...

In this paper, we propose an uplink/downlink duality framework for multi-cell multi-user multiple-input multipleoutput (MU-MIMO) systems with residual hardware impairments (HWIs) at the base station and the user terminals. By employing the proposed uplink/downlink duality framework, complex downlink optimization problems can be transformed to equivalent dual uplink problems which are easier to ...

In a frequency division duplex system, a transmitter adaptive antenna array can potentially improve the performance of a wireless downlink. But because the uplink and downlink channels have different wavelengths, and therefore different responses, direct downlink adaptation based on channel estimates of the uplink is generally not feasible. Instead, there has been some recent interest in adapta...

Recent advances in the speed of multi-rate wireless local area networks (WLANs) and the proliferation of WLAN devices have made rate adaptive, opportunistic scheduling critical for throughput optimization. As WLAN traffic evolves to be more symmetric due to the emerging new applications such as VoWLAN, collaborative download, and peerto-peer file sharing, opportunistic scheduling at the downlin...