The current approach to provide cellular service is for a Mobile Network Operator (MNO) to build and operate its own network. As the density of the deployed devices increases, it becomes necessary to deploy more cells and/or utilize more bandwidth. Finding new sites for deploying new cells is getting increasingly difficult, due to various reasons, such as permitting process, deployment, and operating costs. Utilization of more bandwidth is generally associated with use of higher frequency bands, such as mmW due to the lack of available spectrum in low to mid-band range associated with good capacity coverage tradeoff. Use of mmW for large macro cell sites, may not always result in adequate coverage due to increased losses through modern building materials, tree foliage, rain etc. In this paper, to address the limitations of the current approach, we propose and study a new approach, exploiting sharing and cooperation among UEs. Compared to a typical relaying approach, UE cooperation feature increases radio capabilities of the aggregated devices and could be largely implemented in a manner transparent to the network, allowing the devices to improve Key Performance Indicators (KPIs), such as coverage and capacity, without any further major capital investment in a cellular network.

This paper studies the physical-layer benefits of low latency operation in long-term evolution (LTE) networks. Latency reduction can be achieved by reducing the transmission time interval (TTI) from 1ms to the duration of only a few orthogonal frequency-division multiplexing symbols. The TTI shortening potentially enables faster link adaptation, thereby enhancing system performance. However, enabling low latency operation in a backward compatible manner requires a careful design and performance characterization. This paper conducts a link-level performance analysis of a low latency LTE network in both downlink and uplink with different transmission schemes and under various operating regimes. Our results reveal that a low latency LTE network can provide reasonable link-level performance improvements as compared to a legacy LTE network.

In this paper we consider a heterogeneous LTE network where femto cells are randomly deployed in a macro network. Femto cells are modeled as closed cells, namely only group member UEs can be associated with the femto cells. We demonstrate that inter-cell interference may prevent reliable operations for non-member UEs that are in proximity of a closed cell, which thus experience outage. We show how some of the novel features introduced in the Rel-10 specifications of the LTE standard can be leveraged by a suitable inter-cell interference coordination scheme (ICIC), which relies upon resource partitioning among different nodes to reduce the inter-cell interference problem. Additional significant improvements can be achieved when the proposed ICIC scheme is associated to a simple yet effective autonomous power control algorithm, described in detail in the paper, and further gains are demonstrated for UEs employing interference cancellation of broadcast interfering signals. We finally propose an enhanced ICIC method, based on a tighter coordination between macro and femto nodes, whose significant performance improvements advocate for suitable updates to the future LTE specifications.

In this paper we consider a heterogeneous LTE network where femto cells are randomly deployed in a macro network according to the two models described in [1], namely dual-strip and NxN. Femto cells are modeled as closed cells, namely only group member UEs can be associated with the femto cells. Therefore, dominant interference may be experienced by non-member UEs that are in proximity of a closed cell and leave these UEs in outage. We show geometry performance in a practical deployment, and discuss an autonomous power control method, which allows to dramatically reduce the outage probability, and we evaluate a resource partitioning method between macro and femto cells that further improves the performance of macro users.

In this paper we quantify 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 8 downlink system performance for a macro cell hexagonal grid scenario. The system performance is analyzed for a closed loop Single User Multi-Input Multi Output (SU-MIMO) mode and compared with Single Input Multiple Output (SIMO) and Multi-User (MU) MIMO modes, for a full buffer scenario and static users. In addition to the full buffer scenario, traffic models are considered for SIMO mode to evaluate impact of partial loading and handover. Voice over Internet Protocol (VoIP) system performance is quantified for static users. Mobility simulations are performed for Video Telephony (VT) users and compared to the static case.

This work introduces the enhanced reverse link in Revision D of IS-2000, which is also known as cdma2000 1/spl times/EV-DV. The goals and considerations of the design process are discussed. Design alternatives, choices, and trade-offs are then presented. Finally, the overall operation of the system is examined.

A novel forward link supervision algorithm applicable to power controlled CDMA systems is presented. This new algorithm relies upon the quality of the dedicated power control commands and is therefore compatible with systems that offer packet data service without an assigned dedicated Walsh code channel such as that found in commercial systems denned by IS-2000 Rev C. The algorithm is analyzed both analytically and with simulations. The conclusion from these analyzes show that the proposed forward link supervision algorithm does not affect the call quality, minimizes the impact on the reverse link capacity from unreliable power control commands and leads to call termination only if necessary.

Recently, a novel scheme for iterative multiuser detection and turbo decoding was proposed by the authors (2000). It has been shown that the proposed detector approaches the multiuser capacity limit within 1 dB in the low signal-to-noise ratio region. However, the main drawback of the scheme is its exponential complexity in the number of users, which is due to the complexity of the MAP multiuser detector. In this paper, we show that the complexity of the algorithm can be significantly reduced by employing a greedy multiuser detector. The results for both the additive white Gaussian noise and the single-path fading channels show that the substantial reduction in complexity introduces a slight degradation in performance, 0.5 dB compared to MAP detector.

We propose a novel enhanced closed loop power control scheme applicable to turbo coded packet data transmission. The scheme includes an adaptive outer loop and an outer-outer loop. The outer loop mechanism sets the target signal-to-noise ratio (SNR) for the inner loop so that iterative decoding of the turbo codes is completed after a target number of iterations. The target number of iterations is set by the outer-outer loop so that the desired frame error rate (FER) is achieved. The proposed scheme is directly applicable to code division multiple access (CDMA) mobile stations supporting the IS-2000 standard while operating a forward supplemental channel (F-SCH) with turbo codes.

Previously, a novel scheme for iterative multiuser detection and turbo decoding was proposed by Damnjanovic and Vojcic (2000, 2001). In this scheme, multiuser detection and single-user turbo decoding are tightly coupled to maximize the overall gain. The extrinsic probabilities for the coded bits of the interfering users, obtained after each turbo decoding iteration, are used as a priori probabilities in the following multiuser iteration and the extrinsic information for the systematic bits of the desired user is used as a priori information in the next single-user turbo decoding iteration. Turbo decoding of parallel concatenated convolutional codes is carried out in parallel fashion. It has been shown that the proposed detector approaches the multiuser capacity limit within 1 dB in the low signal-to-noise ratio region. However, the main drawback of the scheme is its exponential complexity in the number of users, which is due to the complexity of the maximum a posteriori probability (MAP) multiuser detector. In this paper, we show that the complexity of the scheme can be significantly reduced by replacing the (MAP) multiuser detector with an iterative detector derived from the greedy multiuser detector proposed by AlRustamani and Vojcic (2000). In this paper, we demonstrate that, for both the additive white Gaussian noise and the frequency-nonselective Rayleigh fading, the substantial reduction in complexity of the iterative scheme proposed by Damnjanovic and Vojcic when the greedy detector is utilized introduces a slight degradation in performance.