Backhaul Connectivity Research Articles

Performance Analysis of Novel Interference Mitigation Schemes in Heterogeneous Networks over Rayleigh and Rician Fading Channels

of Long Term Evolution (LTE) for indoor coverage extension. Heterogeneous networks in which femto and pico-cells are overlaid onto macro-cells are extensively discussed. In order to maintain reliable service of macro-cells, it is important to mitigate destructive femto-femto (co-channel) and femto-macro (adjacent or cross channel) cell interferences respectively. This paper presents the performance analysis of two novel schemes in order to mitigate interference issues in femto-cells. The significant advantage of the proposed femto cooperative (Fe-COPE) scheme is to mitigate co-channel interference that needs no back-haul connection. However, the another proposed Femto Adjacent (FE-ADJ) scheme helps to mitigate adjacent-channel interference and works with coordination of femto and macro base stations by using wired back-haul. The performance is analyzed over independent and identical (i:i:d) Rayleigh and Rician-K fading environments. The closed form expressions for the moment generating function (MGF) of the received signal-to-noise-ratio (SNR) are derived in order to evaluate the average symbol error rate (SER) analysis and then compute the bit error rate (BER) expressions under the M-QAM modulation scheme. Our simulation demonstrates considerable improvement in the curves of BER as a function of SNR. Monte-Carlo simulations are conducted to verify the correctness of the analytical expressions that are derived for the two proposed schemes.

CoMP clustering and backhaul limitations in cooperative cellular mobile access networks

Coordinated Multi-Point (CoMP) transmission and reception is a promising solution for managing interference and increasing performance in future wireless cellular systems. Due to its strict requirements in terms of capacity, latency, and synchronization among cooperating Base Stations (BSs), its successful deployment depends on the capability of the mobile backhaul network infrastructure.We deal with the feasibility of CoMP transmission/reception, in particular of Joint Transmission (JT). For this, we first evaluate which cluster sizes are reasonable from the wireless point-of-view to achieve the desired performance gains. Thereafter, we analyze how different backhaul topologies (e.g., mesh and tree structures) and backhaul network technologies (e.g., layer-2 switching and single-copy multicast capabilities) can support these desired clusters. We study for different traffic scenarios and backhaul connectivity levels, which part of the desired BS clusters are actually feasible according to the backhaul characteristics. We found out that a significant mismatch exists between the desired and feasible clusters. Neglecting this mismatch causes overheads in real JT implementations, which complicates or even prevents their deployment.Based on our findings, we propose a clustering system architecture that not only includes wireless information, as done in the state of the art, but also combines wireless and backhaul network feasibility information in a smart way. This avoids unnecessary signaling and User Equipment (UE) data exchange among BSs which are not eligible to take part in the cooperative cluster. Evaluations show that our scheme reduces the signaling and UE data exchange overhead by up to 85% compared to conventional clustering approaches, which do not take into account the backhaul network’s status.

A mathematical optimization approach for cellular radio network planning with co-siting

Wireless network operators are continuously enhancing their networks by deploying newly developed wireless technologies. In order to reduce the deployment costs, the operators try to reuse as many components of the existing networks as possible. This includes the possibility of reusing base station sites in order to reduce costs such as site rental, site acquisition, and backhaul connectivity. In this paper, we model the problem of base station co-siting as a nested mixed integer optimization problem in order to optimize target objectives that are a function of performance and cost. The formulated problem takes as input an area of interest with existing fixed sites and obtains as output the optimal number and locations of required sites including newly deployed and co-sited with the fixed sites. The goal is to minimize the deployment cost of the new network by reusing as many existing sites of the existing network as possible while guaranteeing that the outage probability is below a target threshold. We propose and implement an algorithm to solve the formulated optimization problem as a function of the mobile station distribution and the existing fixed site locations. A UMTS/GSM co-siting scenario is used as a case study in order to evaluate the performance of the proposed algorithm. Results show that the optimal solution depends on the mobile station distribution and the existing sites in addition to a threshold parameter that provides a tradeoff between the deployment cost and the outage probability.

Performance Evaluation of Multi-Channel Wireless Mesh Networks with Embedded Systems

Many commercial wireless mesh network (WMN) products are available in the marketplace with their own proprietary standards, but interoperability among the different vendors is not possible. Open source communities have their own WMN implementation in accordance with the IEEE 802.11s draft standard, Linux open80211s project and FreeBSD WMN implementation. While some studies have focused on the test bed of WMNs based on the open80211s project, none are based on the FreeBSD. In this paper, we built an embedded system using the FreeBSD WMN implementation that utilizes two channels and evaluated its performance. This implementation allows the legacy system to connect to the WMN independent of the type of platform and distributes the load between the two non-overlapping channels. One channel is used for the backhaul connection and the other one is used to connect to the stations to wireless mesh network. By using the power efficient 802.11 technology, this device can also be used as a gateway for the wireless sensor network (WSN).

Cooperative Network Coding Strategies for Wireless Relay Networks with Backhaul

We investigate cooperative network coding strategies for relay-aided two-source two-destination wireless networks with a backhaul connection between the source nodes. Each source multicasts information to all destinations using a shared relay. We study cooperative strategies based on different network coding schemes, namely, finite field and linear network coding, and lattice coding. To further exploit the backhaul connection, we also propose network coding based beamforming. We measure the performance in term of achievable rates over Gaussian channels, and observe significant gains over benchmark schemes. We derive the achievable rate regions for these schemes and find the cut-set bound for our system. We also show that the cut-set bound can be achieved by network coding based beamforming when the signal-to-noise ratios lie in the sphere defined by the source-relay and relay-destination channel gains.

A new topology for telecom and broad band services in spars, remote and hilly areas

Technological development and mass scale deployment of mobile telephony in the last 15-20 yrs has made telecom services an essential commodity for the modern age society. Affordable and wide spread availability of telecom services is giving impetus to digitalization of all the contents and leading to convergence of telecom, media and broadcasting. This phenomenon is further accelerating the demand for higher bandwidth, while at the same time there is a limitation in the availability of additional spectrum and is posing problems due to increased power consumption by telecom systems, ill effects of excessive electromagnetic radiations and scarcity of backbone for carrying telecom traffic. To overcome the above problems there is a need for defining new topologies for telecom and broadband deployment befitting the terrain and population density, particularly in the thinly populated, remote and hilly areas where making available regular power supply for operating telecom infrastructure round the clock and installing backbone infrastructure in the conventional way is impractical and not cost effective. A study is attempted to define a new telecom network deployment topology that would reduce the power and backbone backup required by almost 50 times while at the same time, increase and make available broadband connectivity on demand and also reduce the ill effect of electromagnetic radiations in a phenomenal manner. The authors have attempted to vary the capacity and coverage, of telecom services provided, based on the requirement, and have also phenomenally increased the coverage provided by the mother BTS by increasing its height by almost 10 times by placing it in a tethered balloon. While this would provide uniform umbrella coverage with low traffic capacity over a large area i.e., upto 5000 Sq Kms, enhanced capacity would be provided in pockets under this umbrella in populated residential area (villages) and office complexes by installing very low power BTSs which are equivalent system capable of being operated using alternate sources of energy like wind, solar etc and also cause negligible electromagnetic radiation pollution. The umbrella coverage provided by the mother BTS will communicate with these low power BTSs and will also provide backhaul connectivity.

Challenges for Wireless Mesh Networks to provide reliable carrier-grade services

Abstract. Provision of mobile and wireless services today within a competitive environment and driven by a huge amount of steadily emerging new services and applications is both challenge and chance for radio network operators. Deployment and operation of an infrastructure for mobile and wireless broadband connectivity generally requires planning effort and large investments. A promising approach to reduce expenses for radio access networking is offered by Wireless Mesh Networks (WMNs). Here traditional dedicated backhaul connections to each access point are replaced by wireless multi-hop links between neighbouring access nodes and few gateways to the backbone employing standard radio technology. Such a solution provides at the same time high flexibility in both deployment and the amount of offered capacity and shall reduce overall expenses. On the other hand currently available mesh solutions do not provide carrier grade service quality and reliability and often fail to cope with high traffic load. EU project CARMEN (CARrier grade MEsh Networks) was initiated to incorporate different heterogeneous technologies and new protocols to allow for reliable transmission over "best effort" radio channels, to support a reliable mobility and network management, self-configuration and dynamic resource usage, and thus to offer a permanent or temporary broadband access at high cost efficiency. The contribution provides an overview on preliminary project results with focus on main technical challenges from a research and implementation point of view. Especially impact of mesh topology on the overall system performance in terms of throughput and connection reliability and aspects of a dedicated hybrid mobility management solution will be discussed.

Handover Scheme in LTE-based Networks with Hybrid Access Mode

Femtocell networks that use Home evolved NodeB (HeNB) and existing networks for backhaul connectivity can fulfill the upcoming demand for high data rates in wireless communication systems as well as extend the coverage area. We consider some parameters for handovers, including interference, velocity, RSS and quality of service (QoS) level. We propose a new handover strategy between the femtocell and the macrocell for LTE (Long Term Evolution) -based networks in hybrid access mode. This strategy can avoid unnecessary handovers and can reduce handover failure. In this paper, we analyze three scenarios for handover decision strategy procedures: hand-in for Closed Subscriber Groups, hand-in for non-Closed Subscriber Groups, and hand-out.

Mango: Low-cost, scalable delivery of rich content on mobile devices

We present mango, a novel low-cost and highly scalable content delivery service for mobile phones. The service is targeted at emerging countries such as India where users are highly price sensitive, and there is considerable demand for rich media content. mango is designed as a content “synch-up” service. Users install an application (app) on the phone, and through a simple menu select content for download, upload, or sharing. Then, in order to actually transfer content to and from their phones, users visit or opportunistically connect with mango hotspots. The hotspots are short range cells (installed in shops, cafes, or as an app in other users' phones) with a backhaul connection and a wireless interface (such as Bluetooth/Wi-Fi, and down the road femtocells) to communicate with the phones. Given a large number of such low-cost, short range access points, the mango network delivers content to the very edge of the network, within a few feet from the user. Such a content delivery architecture is faster, cheaper, and can support a much larger number of users than macrocellular data networks. In this paper we present the mango service architecture, discuss technical challenges to shorten download times and lower content delivery costs, and outline our plans to develop and deploy this service. We also discuss a variety of interesting applications and services that can be deployed over the core mango system.

Optimal resource allocation for relay-assisted wireless communication systems

The design, analysis and optimization of cooperative/relaying communication systems have recently become a very active research area within both the information theory as well as communications engineering societies. It is now well understood that relaying strategies can improve the coverage of wireless networks by providing higher data rates or better transmission reliability to user terminals at the edge of a wireless cell, or terminals having faded connectivity with the base station. Relaying technologies are also becoming part of the telecommunication standards. Although we can find studies, in the academic literature, on advanced relaying schemes, which are based on user terminals cooperating to help each other while applying decentralized resource allocation strategies, the first actual deployment step which will take place within the 3GPP long-term evolution (LTE)-advanced standard is based on fixed access points to do the relaying and within a centralized scheme in which the e-nodeB (base station with backhaul connection) takes the scheduling and resource allocation decisions. One major objective in 3GPP evolution is to utilize the scarce wireless system resources efficiently because achieving the high quality of service (QoS) targets through over-provisioning is uneconomical due to the relatively high cost for transmission capacity in cellular access networks. Our objective here is to obtain the optimal (from an information theory perspective) resource allocation schemes taking into considerations the system constraints that are relevant to the LTE-advanced standard. We have been able to derive optimal resource allocation polices that are provably based on closed-form formulations which are practical for implementation. They include the policies for (i) transmission mode selection (i.e. deciding whether the user needs the assistance of a relay or not), (ii) power allocation for the base station and the relays, and (iii) criterion for user scheduling over the available air-link resource units. Simulation results demonstrate that our proposed resource allocation scheme provides considerable throughput gains especially for users receiving low power through the direct link with the base station.

Cell Association and Interference Coordination in Heterogeneous LTE-A Cellular Networks

Embedding pico/femto base-stations and relay nodes in a macro-cellular network is a promising method for achieving substantial gains in coverage and capacity compared to macro-only networks. These new types of base-stations can operate on the same wireless channel as the macro-cellular network, providing higher spatial reuse via cell splitting. However, these base-stations are deployed in an unplanned manner, can have very different transmit powers, and may not have traffic aggregation among many users. This could potentially result in much higher interference magnitude and variability. Hence, such deployments require the use of innovative cell association and inter-cell interference coordination techniques in order to realize the promised capacity and coverage gains. In this paper, we describe new paradigms for design and operation of such heterogeneous cellular networks. Specifically, we focus on cell splitting, range expansion, semi-static resource negotiation on third-party backhaul connections, and fast dynamic interference management for QoS via over-the-air signaling. Notably, our methodologies and algorithms are simple, lightweight, and incur extremely low overhead. Numerical studies show that they provide large gains over currently used methods for cellular networks.

Security analysis of wireless mesh backhauls for mobile networks

Radio links are used to provide backhaul connectivity for base stations of mobile networks, in cases in which cable-based alternatives are not available and cannot be deployed in an economic or timely manner. While such wireless backhauls have been predominantly used in redundant tree and ring topologies in the past, mobile network operators have become increasingly interested in meshed topologies for carrier-grade wireless backhauls. However, wireless mesh backhauls are potentially more susceptible to security vulnerabilities, given that radio links are more exposed to tampering and given their higher system complexity. This article extends prior security threat analyses of 3rd generation mobile network architectures for the case of wireless mesh backhauls. It presents a description of the security model for the considered architecture and provides a list of the basic assumptions, security objectives, assets to be protected and actors of the analysis. On this foundation, potential security threats are analyzed and discussed and then assessed for their corresponding risk. The result of this risk assessment is then used to define a set of security requirements. Finally, we give some recommendations for wireless mesh backhaul designs and implementations following these requirements.

Utility-based Rate Allocation Scheme for Mobile Video Streaming over Femtocell Networks

This paper proposes a utility-based data rate allocation algorithm to provide high-quality mobile video streaming over femtocell networks. We first derive a utility function to calculate the optimal data rates for maximizing the aggregate utilities of all mobile users in the femtocell. The total sum of optimal data rates is limited by the link capacity of the backhaul connections. Furthermore, electromagnetic cross-talk poses a serious problem for the backhaul connections, and its influence passes on to mobile users, as well as causing data rate degradation in the femtocell networks. We also have studied a fixed margin iterative water-filling algorithm to achieve the target data rate of each backhaul connection as a counter-measure to the cross-talk problem. The results of our simulation show that the algorithm is capable of minimizing the transmission power of backhaul connections while guaranteeing a high overall quality of service for all users of the same binder. In particular, it can provide the target data rate required to maximize user satisfaction with the mobile video streaming service over the femtocell networks.

Doing time [mobile communication

Mobile operators are having to find new ways of synchronising their base station networks as they shift to packet-based backhaul connections. This paper explores their options.

Metropolitan-scale Wi-Fi mesh networks

Standardization, widespread vendor adoption, low cost, and ease of use have all contributed to the explosive growth in Wi-Fi (IEEE 802.11) wireless broadband networks. Wi-Fi access is now available on most notebook computers and personal digital assistants. However, the limited reach of Wi-Fi propagation and high cost of installing and maintaining a wired network backhaul connection have limited Wi-Fi network deployments to homes, offices, public hot spots, and some wide-area hot zones. In addition, installing, managing, and scaling multiple hot spots is difficult. Dense-cellular Wi-Fi mesh networking has the potential to bridge this digital divide, foster economic development, increase public safety organizations' efficiency and effectiveness, and connect communities. The technology is making it possible, for the first time, to create truly unwired cities.