Linear Cellular Networks Research Articles

Uplink outage performance of linear cellular networks with non‐uniform user distribution

The Wyner model has been extensively used in the literature for analysing cellular networks. Recent studies show that when compared with a grid-based model, this simple model fails to capture key features of a cellular network under different scenarios. Without increasing complexity, a linear network model which uses an average user distance and considers a non-uniform user distribution scenario within cells is proposed. Simulation results show that despite the simplicity, the proposed model can provide a close insight when compared with a grid-based model.

Online multi-coloring on the path revisited

Multi-coloring on the path is a model for frequency assignment in linear cellular networks. Two models have been studied in previous papers: calls may either have finite or infinite duration. For hexagonal networks, a variation of the models where limited frequency reassignment is allowed has also been studied. We add the concept of frequency reassignment to the models of linear cellular networks and close these problems by giving matching upper and lower bounds in all cases. We prove that no randomized algorithm can have a better competitive ratio than the best deterministic algorithms. In addition, we give an exact characterization of the natural greedy algorithms for these problems. All of the above results are with regard to competitive analysis. Taking steps towards a more fine-grained analysis, we consider the case of finite calls and no frequency reassignment and prove that, even though randomization cannot bring the competitive ratio down to one, it seems that the greedy algorithm is expected optimal on uniform random request sequences. We prove this for small paths and indicate it experimentally for larger graphs.

Linear Precoding Bounds for Wyner-Type Cellular Networks With Limited Base-Station Cooperation and Dynamic Clustering

This work studies the achievable average data rate in the downlink of a Wyner-type linear cellular network with limited cooperation and linear precoders. We derive upper and lower bounds on the achievable average data rate subject to an average power constraint. The bounds show that even a small number of cooperating base stations applying suboptimal (linear) precoding can approach optimal performance, and significantly increase the average user data rates as compared to those achievable with noncooperating cellular systems. We highlight the importance of dynamic clustering and of base station (BS) silencing. Dynamic clustering allows the system to build clusters that benefit some users at the expense of others, and then shifts the priority between the users. Such a scheme results in higher average rates for all users, while meeting some level of fairness. BS silencing is shown to be important for limited cooperation networks in the high SNR regime. Silencing is a simple and efficient way to reduce the interference (and hence increase the user rates) without increasing the number of cooperating BSs. The theoretical analysis is accompanied by several numerical examples in selected scenarios.

Deterministic on-line call control in cellular networks

We study an on-line call control problem in cellular networks that are based on the Frequency Division Multiplexing (FDM) technology. In such networks, interference may occur when the same frequency is assigned to two different calls emanating from the same cell or its neighboring cells. The number of frequencies supporting the networks is limited. The goal is to maximize the number of calls served without causing any interference. We focus on the case that the number of frequencies is sufficiently large and the calls stay forever. We give a deterministic on-line algorithm with asymptotic competitive ratio of 2.5 and show a general lower bound of 2. For the special case of linear cellular networks, we achieve a best possible deterministic on-line algorithm with asymptotic competitive ratio of 3/2.

Three results on frequency assignment in linear cellular networks

In the frequency assignment problem we are given a graph representing a wireless network and a sequence of requests, where each request is associated with a vertex. Each request has two more attributes: its arrival and departure times, and it is considered active from the time of arrival to the time of departure. We want to assign frequencies to all requests so that at each time step any two active requests associated with the same or adjacent vertices use different frequencies. The objective is to minimize the number of frequencies used. We focus exclusively on the special case of the problem when the underlying graph is a linear network (path). For this case, we consider both the offline and online versions of the problem, and we present three results. First, in the incremental online case, where the requests arrive over time, but never depart, we give an algorithm with an optimal (asymptotic) competitive ratio 4 3 . Second, in the general online case, where the requests arrive and depart over time, we improve the current lower bound on the (asymptotic) competitive ratio to 11 7 . Third, we prove that the offline version of this problem is N P -complete.

Local Base Station Cooperation Via Finite-Capacity Links for the Uplink of Linear Cellular Networks

Cooperative decoding at the base stations (or access points) of an infrastructure wireless network is currently well recognized as a promising approach for intercell interference mitigation, thus enabling high frequency reuse. Deployment of cooperative multicell decoding depends critically on the tolopology and quality of the available backhaul links connecting the base stations. This work studies a scenario where base stations are connected only if in adjacent cells, and via finite-capacity links. Relying on a linear Wyner-type cellular model with no fading, achievable rates are derived for the two scenarios where base stations are endowed only with the codebooks of local (in-cell) mobile stations, or also with the codebooks used in adjacent cells. Moreover, both uni- and bidirectional backhaul links are considered. The analysis sheds light on the impact of codebook information, decoding delay, and network planning (frequency reuse) on the performance of multicell decoding as enabled by local and finite-capacity backhaul links. Analysis in the high-signal-to-noise ratio (SNR) regime and numerical results validate the main conclusions.

Joint Optimal Access Point Selection and Channel Assignment in Wireless Networks

In wireless cellular networks or in other networks with single-hop communication, the fundamental access control problem pertains to access point (AP) selection and channel allocation for each user. For users in the coverage area of one AP, this involves only channel allocation. However, users that belong in the intersection of coverage areas of more than one AP can select the appropriate AP to establish connection and implicitly affect the channel assignment procedure. We address the joint problem of AP selection and channel assignment with the objective to satisfy a given user load vector with the minimum number of channels. Our major finding is that the joint problem reduces to plain channel allocation in a cellular network that emerges from the original one after executing an iterative and provably convergent clique load balancing algorithm. For linear cellular networks, our approach leads to minimum number of required channels to serve a given load vector. For 2D cellular networks, the same approach leads to a heuristic algorithm with a suboptimal solution due to the fact that clique loads cannot be balanced. Numerical results demonstrate the performance benefits of our approach in terms of blocking probability in a dynamic scenario with time-varying number of connection requests. The presented approach constitutes the basis for addressing more composite resource allocation problems in different context.