Load Balancing is typically used in cellular wireless networks in the frequency domain to balance paging, access, and traffic load across the available bandwidth. In this paper we extend the concept of Load Balancing to the Spatial domain. We develop two approaches - Network Load Balancing and Single-Carrier MultiLink - for Spatial Load Balancing. While these techniques are applicable to both cellular wireless networks and WiFi networks we illustrate them on EV-DO (a 3G cellular data network). Both these methods apply when the device has more than one candidate server and determine the server(s) using not only the channel quality from the server to the device but also the current load on each server. The proposed techniques leverage existing cellular (EV-DO) network architecture and are fully backward compatible. Network operators can realize both a substantial increase in network capacity and deliver a notable improvement in user experience by applying these techniques. The combination of load balancing in the frequency domain (Smart Carrier Management and multi-carrier) and spatial domain improves the connectivity within a network, enabling an optimal allocation of resources under the p-fair criterion.

We pose a network-wide scheduling problem for cellular wireless networks in which users are capable of being served by several schedulers on the downlink, though not jointly. We present a distributed algorithm, with limited communication across servers, that solves this problem optimally, in that it gives the network-wide proportional fair solution. An idealized version is presented first, in which all users are capable of being served by all schedulers and in which all the decision-making takes place among the schedulers alone. A practical version is also presented, in which users play a role in choosing their servers and servers decide how to allocate resources to the users that choose them. The practical version can achieve the same optimum as the idealized one and gives gains up to 60% in typical network deployments. This version can be implemented on any wireless technology to achieve optimal network scheduling. We have focused particularly on LTE, HSPA and 1xEV-DO and the first commercial deployment will soon occur on the 1xEV-DO system, based on the 3GPP2 standard, under the rubric of `Smart Networks.

- This paper presents a comparison between CDMA and SC-FDMA for reverse link (RL) cellular voice and data communications. The comparison is based on CDMA2000 1x (circuit-switched voice), CDMA2000 1xEV-DO (packet data) and 3GPP LTE Release 8 (SC-FDMA based packet voice and data). We illustrate various modes of LTE system operation and associated trade-offs. For the comparison of data communications we introduce the concept of a "feasible region" that simultaneously captures the system throughput and fairness for a data system. Our simulations based on 3GPP2 evaluation methodology indicate that CDMA2000 1x Revision E capacity (defined as number of simultaneous voice calls per cell) is more than 2X that of LTE Release 8 and air-link latency of the CDMA2000 1x Revision E system is approximately 50% lower (normalized to available spectrum). We also show that the CDMA2000 1xEV-DO Revision A system without interference cancellation (IC) is comparable to the LTE system while the 1xEV-DO system with IC far outperforms the LTE system.

We propose a new model of wireless networks which we refer to as "two-scale networks." At a local scale, characterised by nodes being within a distancer, channel strengths are drawn independently and identically from a distance-independent distribution. At a global scale, characterised by nodes being further apart from each other than a distance r, channel connections are governed by a Rayleigh distribution, with the power satisfying a distance-based decay law. Thus, at a local scale, channel strengths are determined primarily by random effects such as obstacles and scatterers whereas at the global scale channel strengths depend on distance. For such networks, we propose a hybrid communications scheme, combining elements of distance-dependent networks and random networks. For particular classes of two-scale networks withNnodes, we show that an aggregate throughput that is slightly sublinear inN, for instance, of the formN/log4Nis achievable. This offers a significant improvement over a throughput scaling behaviour ofO(√(N))that is obtained in other work.

In many problems in wireline networks, it is known that achieving capacity on each link or subnetwork is optimal for the entire network operation. In this paper, we present examples of wireless networks in which decoding and achieving capacity on certain links or subnetworks gives us lower rates than other simple schemes, like forwarding. This implies that the separation of channel and network coding that holds for many classes of wireline networks does not, in general, hold for wireless networks. Next, we consider Gaussian and erasure wireless networks where nodes are permitted only two possible operations: nodes can either decode what they receive (and then re-encode and transmit the message) or simply forward it. We present a simple greedy algorithm that returns the optimal scheme from the exponential-sized set of possible schemes. This algorithm will go over each node at most once to determine its operation, and hence, is very efficient. We also present a decentralized algorithm whose performance can approach the optimum arbitrarily closely in an iterative fashion

We propose a new model of wireless networks which we refer to as "two-scale networks". At a local scale, characterized by nodes being within a distance r, channel strengths are drawn independently and identically from a distance-independent distribution. At a global scale, characterized by nodes being further apart from each other than a distance r, channel connections are governed by a Rayleigh distribution, with the power satisfying a distance-based decay law. Thus, at a local scale, channel strengths are determined primarily by random effects such as obstacles and scatterers whereas at the global scale channel strengths depend on distance. For such networks, we propose a hybrid communications scheme, combining elements of P. Gupta et al. (2000) (for distance-dependent networks) and R. Gowaikar et al. (2006) (for random networks). For a particular class of two-scale networks with N nodes, we show that an aggregate throughput of the form N[1divide(t-1)]/log2N is achievable, where t > 2 is a parameter that depends on the distribution of the connection at the local scale and is independent of the decay law that operates at a global scale. For t < 3, this offers a significant improvement over the O(radicN) results of P. Gupta et al. (2000)

In this paper, a special class of wireless networks, called wireless erasure networks, is considered. In these networks, each node is connected to a set of nodes by possibly correlated erasure channels. The network model incorporates the broadcast nature of the wireless environment by requiring each node to send the same signal on all outgoing channels. However, we assume there is no interference in reception. Such models are therefore appropriate for wireless networks where all information transmission is packetized and where some mechanism for interference avoidance is already built in. This paper looks at multicast problems over these networks. The capacity under the assumption that erasure locations on all the links of the network are provided to the destinations is obtained. It turns out that the capacity region has a nice max-flow min-cut interpretation. The definition of cut-capacity in these networks incorporates the broadcast property of the wireless medium. It is further shown that linear coding at nodes in the network suffices to achieve the capacity region. Finally, the performance of different coding schemes in these networks when no side information is available to the destinations is analyzed

A network of nodes in which pairs communicate over a shared wireless medium is analyzed. We consider the maximum total aggregate traffic flow possible as given by the number of users multiplied by their data rate. The model in this paper differs substantially from the many existing approaches in that the channel connections in this network are entirely random: rather than being governed by geometry and a decay-versus-distance law, the strengths of the connections between nodes are drawn independently from a common distribution. Such a model is appropriate for environments where the first-order effect that governs the signal strength at a receiving node is a random event (such as the existence of an obstacle), rather than the distance from the transmitter. It is shown that the aggregate traffic flow as a function of the number of nodes n is a strong function of the channel distribution. In particular, for certain distributions the aggregate traffic flow is at least n/(logn)/sup d/ for some d>0, which is significantly larger than the O(/spl radic/n) results obtained for many geometric models. The results provide guidelines for the connectivity that is needed for large aggregate traffic. The relation between the proposed model and existing distance-based models is shown in some cases.

We analyze a network of nodes in which pairs communicate over a shared wireless medium. We are interested in the maximum total aggregate traffic flow that is possible through the network. Our model differs substantially from the many existing approaches in that the channel connections in our network are entirely random: we assume that, rather than being governed by geometry and a decay law, the strength of the connections between nodes is drawn independently from a common distribution. Such a model is appropriate for environments where the first order effect that governs the signal strength at a receiving node is a random event (such as the existence of an obstacle), rather than the distance from the transmitter. We show that the aggregate traffic flow is a strong function of the channel distribution. In particular, we show that for certain distributions, the aggregate traffic flow scales at least as n/(log n)vfor some fixed v > 0, which is significantly larger than the O(radic/n) results obtained for many geometric models

We determine the capacity of a certain class of wireless erasure relay networks. We first find a suitable definition for the "cut-capacity" of erasure networks with broadcast at transmission and no interference at reception. With this definition, a maxflow mincut capacity result holds for the capacity of these networks.

In many communications problems, maximum-likelihood (ML) decoding reduces to finding the closest (skewed) lattice point in N-dimensions to a given point x/spl isin/C/sup N/. In its full generality, this problem is known to be NP-complete and requires exponential complexity in N. Recently, the expected complexity of the sphere decoder, a particular algorithm that solves the ML problem exactly, has been computed; it is shown that, over a wide range of rates, SNRs and dimensions, the expected complexity is polynomial in N. We propose an algorithm that, for large N, offers substantial computational savings over the sphere decoder, while maintaining performance arbitrarily close to ML. The method is based on statistically pruning the search space. Simulations are presented to show the algorithm's performance and the computational savings relative to the sphere decoder.