Super-resolution broad null beamforming for cochannel interference cancellation in mobile radio networks

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RF Coverage Planning And Analysis With Adaptive Cell Sectorization In Millimeter Wave 5G Networks

The advancement of Fifth Generation Network (5G) technology is well underway, with Mobile Network Operators (MNOs) globally commencing the deployment of 5G networks within the mid-frequency spectrum range (3GHz–6GHz). Nevertheless, the escalating demands for data traffic are compelling MNOs to explore the high-frequency spectrum (24GHz–100GHz), which offers significantly larger bandwidth (400MHz-800 MHz) compared to the mid-frequency spectrum (3GHz–6GHz), which typically provides 50MHz-100MHz of bandwidth. However, it is crucial to note that the higher-frequency spectrum imposes substantial challenges due to exceptionally high free space propagation loss, resulting in 5G cell site coverage being limited to several hundred meters, in contrast to the several kilometers achievable with 4G. Consequently, MNOs are faced with the formidable task of accurately planning and deploying hundreds of new 5G cells to cover the same areas served by a single 4G cell.This dissertation embarks on a comprehensive exploration of Radio Frequency (RF) coverage planning for 5G networks, initially utilizing a conventional three-sector cell architecture. The coverage planning phase reveals potential challenges, including coverage gaps and poor Signal-to-Interference-plus-Noise Ratio (SINR). In response to these issues, the dissertation introduces an innovative cell site architecture that embraces both nine and twelve sector cells, enhancing RF coverage through the adoption of an advanced antenna system designed with subarrays, offering adaptive beamforming and beam steering capabilities. To further enhance energy efficiency, the dissertation introduces adaptive higher-order cell-sectorization (e.g., nine sector cells and twelve sector cells). In this proposed method, all sectors within a twelve-sector cell remain active during peak hours (e.g., daytime) and are reduced to fewer sectors (e.g., nine sectors or six sectors per cell) during off-peak hours (e.g., nighttime). This dynamic adjustment is facilitated by an advanced antenna system utilizing sub-array architecture, which employs adaptive beamforming and beam steering to tailor the beamwidth and radiation angle of each active sector. Simulation results unequivocally demonstrate significant enhancements in RF coverage and SINR with the implementation of higher-order cell-sectorization. Furthermore, the proposed adaptive cell-sectorization method significantly reduces energy consumption during off-peak hours. In addition to addressing RF coverage planning, this dissertation delves into the numerous challenges associated with deploying 5G networks in the higher frequency spectrum (30GHz-300GHz). It encompasses issues such as precise cell site planning, location acquisition, propagation modeling, energy efficiency, backhauling, and more. Furthermore, the dissertation offers valuable insights into future research directions aimed at effectively surmounting these challenges and optimizing the deployment of 5G networks in the high-frequency spectrum

Joint array combining and MLSE for single-user receivers in multipath Gaussian multiuser channels

The well-known structure of an array combiner along with a maximum likelihood sequence estimator (MLSE) receiver is the basis for the derivation of a space-time processor presenting good properties in terms of co-channel and intersymbol interference rejection. The use of spatial diversity at the receiver front-end together with a scalar MLSE implies a joint design of the spatial combiner and the impulse response for the sequence detector. This is faced using the MMSE criterion under the constraint that the desired user signal power is not cancelled, yielding an impulse response for the sequence detector that is matched to the channel and combiner response. The procedure maximizes the signal-to-noise ratio at the input of the detector and exhibits excellent performance in realistic multipath channels.Peer Reviewe

Adaptive space-time processing for digital mobile radio communication systems

The performance of digital mobile radio communication systems is primarily limited by cochannel interference and multipath fading. Antenna arrays, with optimum combining (OC), have been shown to combat multipath fading of the desired signal and are capable of reducing the power of interfering signals at the receiver through spatial filtering. With OC, the signals received by several antenna elements are weighted and combined to maximize the output signal-to-interference-plus-noise ratio (SLNR). We derive new closed-form expressions for (1) the probability density function (PDF) of the SINR at the output of the optimum combiner, (2) the average probability of bit error rate (BER) and its upper bound, and (3) the outage probability in a Rayleigh fading environment with multiple cochannel interferers. The study covers both the case when the number of antenna elements exceeds the number of interferers and vice versa. We consider independent fading at each antenna element, as well as the effect of fading correlation. The analysis is also extended to processing using maximal ratio combining (MRC). The performance of the optimum combiner is compared to that of the maximal ratio combiner and results show that OC performs significantly better than MRC. We investigate the performance of OC in a microcellular environment where the desired signal and the cochannel interference can have different statistical characteristics. The desired signal is assumed to have Rician statistics implying that a dominant multipath reflection or a line-of-sight (LOS) propagation exists within-cell transmission. Interfering signals from cochannel cells are assumed to be subject to Rayleigh fading due to the absence of LOS propagation. This is the so called Rician/Rayleigh model. We also study OC for a special case of the Rician/Rayleigh model, the Nonfading/Rayleigh model. We derive expressions for the PDF of the SJNR, the BER and the outage probability for both Rician/Rayleigh and Nonfading/Rayleigh models. Similar expressions are derived with MRC. Another area in which space-time processing may provide significant benefits is when wideband signals (such as code division multiple access (CDMA) signals) are overlaid on existing narrowband user signals. The conventional approach of rejecting narrowband interference in direct-sequence (DS) CDMA systems has been to sample the received signal at the chip interval, and to exploit the high correlation between the interference samples prior to spread spectrum demodulation. A different approach is space-time processing. We study two space-time receiver architectures, referred to as cascade and joint, respectively, and evaluate the performance of a DS-CDMA signal overlaying a narrowband signal for personal communication systems (PCS). We define aild evaluate the asymptotic efficiency of each configuration. We develop new closed-form expressions for the PDF of the SINR at the array output, the BER and its upper bound, for both cascade and joint configurations. We also analyze the performance of this system in the presence of multiple access interference (MAJ)

The Impact of Space Division Multiplexing on Resource Allocation: A Unified Approach

Recent advances in the area of wireless communications have revealed the emerging need for efficient wireless access in personal, local and wide area networks. Space division multiple access (SDMA) with smart antennas at the base station is recognized as a promising means of increasing system capacity and supporting rate-demanding services. However, the existence of SDMA at the physical layer raises significant issues at higher layers. In this paper, we attempt to capture the impact of SDMA on channel allocation at the media access control (MAC) layer. This impact obtains different forms in TDMA, CDMA and OFDMA access schemes, due to the different cochannel and inter-channel interference instances, as well as the different effect of corresponding channels (time slots, codes or subcarrier frequencies) on user channel characteristics. We follow a unified approach for these multiple access schemes and propose heuristic algorithms to allocate channels to users and adjust down-link beamforming vectors and transmission powers, with the objective to increase achievable system rate and provide QoS to users in the form of minimum rate guarantees. We consider the class of greedy algorithms, based on criteria such as minimum induced or received interference and minimum signal-to-interference ratio (SIR), as well as the class of SIR balancing algorithms. Our results indicate that this cross-layer approach yields significant performance benefits and that SIR balancing algorithms achieves the best performance

Reduced cost alternatives to premise wiring using ATM and microcellular technologies

The cost of premises wiring keeps increasing due to personnel moves, new equipment, capacity upgrades etc. It would be desirable to have a wireless interface from the workstations to the fixed network, so as to minimize the wiring changes needed. New technologies such as microcellular personal communication systems are promising to bring down the cost of wireless communication. Another promising technology is Code Division Multiple Access (CDMA), which could dramatically increase the bandwidth available for wireless connections. In addition, Asynchronous Transfer Mode (ATM) technology is emerging as a technique for integrated management of voice, data, and video traffic on a single network. The focus of this investigation will be to assess the future utility of these new technologies for reducing the premise wiring cost at KSC. One of the issues to be studied is the cost comparison of 'old' versus 'new,' especially as time and technology progress. An additional issue for closer study is a feasible time-line for progress in technological capability