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  • 1.
    Lungaro, Pietro
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Timus, Bogdan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Cost Analysis of Wireless Multihop Architectures2004Conference paper (Refereed)
    Abstract [en]

    Previous studies have shown that multihop techniques  can improve the capacity/coverage of a hybrid cellular  system, but the economic gain is still an open question. An  infrastructure cost analysis is performed in this paper on two  hybrid cellular architectures: one using terminals as relays and  one using fixed relays.

    For the first architecture we show numerical examples in which  the infrastructure cost is 20% to 40% higher when multihopping  is not used. The size of the gain depends on the density of relaying  terminals. For the second architecture the cost ratio between  deploying a new macro base station and deploying a wireless  relay. In the selected examples, the infrastructure cost is 25%  to 100% higher when multihopp is not used, for a cost ratio  between a macro base station and a relay varying from 20 to 34.

  • 2.
    Nordmark, Hannes
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Non Regenerative Cooperative MIMO Relaying - A Radio Network Capacity Evaluation2005Conference paper (Refereed)
    Abstract [en]

    The concept of Cooperative MIMO Relaying (CMIMOR)  has previously been introduced in order to allow terminals  with single antenna elements to take some advantage of the  MIMO techniques. In this paper we evaluate the capacity  of a radio network employing non regenerative CMIMOR  connections by explicitly taking into account the amount  of additional resources needed for relaying. The paper investigates  both a centralised and a decentralised resource  allocation algorithm. We show that with a tight resource  reuse, which is accomplished with the decentralised algorithm,  and high relay densities, the CMIMOR system  yields capacity figures superior to a single hop system employing  beamforming. The gains are expressed in terms of  average system capacity.

  • 3.
    Timus, Bogdan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A Cost Model for Ad Hoc Extended Cellular Systems2004Conference paper (Refereed)
    Abstract [en]

    The use of ad hoc/multihop as an extension to the cellular system has been proposed in the literature as a candidate architecture for providing lower infrastructure costs. In this paper the base station and wireless relay density are used as the main measures for the infrastructure cost. An analytical expression is deduced for the relation between the base station and the wireless relay densities. It is shown that, under some circumstances, the same service can be provided to the end-user with a reduced base station density if wireless relays (routers) are used for multihopping, thus reducing the infrastructure cost. However, the base station density can not be made arbitrarily low due to the increase in the transport traffic and the well-known Shannon limit on the channel capacity.

  • 4.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    A Coverage Analysis of Amplify-and-Forward Relaying Schemes in Outdoors Urban Environment2006In: Wireless and Mobile Communications, 2006. ICWMC '06. International Conference on Wireless and Mobile Communications, IEEE , 2006, p. 56-Conference paper (Refereed)
    Abstract [en]

    The use of cellular systems enhanced by fixed relayshas previously been proposed as a way to provide wide areacoverage for high bit-rate at a reduced cost of the wireless accessnetwork. In this paper1 three amplify-and-forward relayingschemes are analysed on the downlink, in a scenario where95% coverage has to be provided for a predefined bit-rate in atypical urban environment. Numeric results show that combiningdiversity, such as SIMO has only marginal gains over selectiondiversity when only one relay is used. The use of transmissiondiversity for the MIMO relaying scheme reduces the base stationdensity, but the relaying gain is comparable with the onesfor selection and SIMO. With the random (unplanned) relaydeployment considered in this study, 0.03 to 0.15 base stationsare saved for each deployed relay. This means that the cost of arelay can be at most 3 to 15% the cost of a base station. Thehighest reduction is achieved when micro base stations are used.

  • 5.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Break-Even Costs in a Cellular Multihop System with Fixed Relays2005Conference paper (Refereed)
    Abstract [en]

    This paper extends some previous work on the economical feasibility of a cellular multihop system with fixed relays (mesh network) by considering link adaptation. The results are expressed in terms of the break-even cost, which is an upper bound on how expensive a relay can be with respect to a base station. For a system with few hops, the break-even cost is about the same (6-9%) with both fixed and variable link rate. The introduction of a STDMA scheme based on proportional fair scheduling increases the channel reuse factor from 1.5 to 2.5 times per cell in a hybrid with one relay tier. However it does not improve the break-even cost and it introduces bit-rate unfairness in the service delivery.

  • 6.
    Timus, Bogdan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Cost analysis for an ad hoc extended cellular systems in a rural environment2004Conference paper (Refereed)
    Abstract [en]

    This paper applies two different cost models in order to analyze the infrastructure cost of a communication network in which fixed relays are used for an ad hoc extension of a cellular system. The analysis consists of two parts: solving a dimensioning problem and minimizing the investment cost according to one of the cost models, respectively. For the dimensioning problem, the simple system model introduced in [1] is used. Unlike [1], where some approximations are used to obtain an analytical expression of the interference level, the average cell power is computed in this paper though simulations. Due to the simple propagation models assumed, the model is basically suited for a rural environment.

    According to the simulation results, the analytical modeling in [1] underestimates the cell radius by up to 10%, which means that the infrastructure costs obtained in [1] for this simple system model are overestimated. When using a linear cost model, the analysis shows that the ad hoc extension reduces the infrastructure cost of a purely cellular system if the ratio between the cost of a base station and that of a wireless relay is at least 34. The use of a non linear model, which takes into account the type of the base station, shows more significant cost reductions, even if the cost ratio is as low as 20. All the evaluations consider only the investment costs and apply to loads up to 500 kbps/km2.

  • 7.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Cost Analysis Issues in a Wireless Multihop Architecture with Fixed Relays2005In: VTC2005-SPRING: 2005 IEEE 61ST VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, PROCEEDINGS, New York: IEEE , 2005, p. 3178-3182Conference paper (Refereed)
    Abstract [en]

    The infrastructure costs of a hybrid cellular-multihop and a traditional single-hop cellular system are compared in this paper with the help of a linear cost model. The cost is evaluated in a greenfield operator scenario most suited in a suburban type of environment, by defining a desired service level as achieved bit-rate per area unit [kbps/km2]. The hybrid system consists of macro base stations and fixed wireless routers. The impact of the radio resource allocation scheme on the cost is exemplified with schemes: a cell-based TDMA scheme and a centralized STDMA scheme. Numerical results show that the hybrid system outperforms the traditional one in terms of infrastructure cost if the STDMA scheme is used and if the cost of a relay is 3 to 7% of the macro base station cost, depending on the desired service level.

  • 8.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Coverage costs of one amplify-and-forward relaying in outdorrs urban environment2006In: Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, IEEE , 2006, p. 1-5Conference paper (Refereed)
    Abstract [en]

    The use of fixed relays has previously been shown to enhance the performance of cellular systems, e.g. in terms of improved bit-rate CDFs. Under the assumption that these relays are inexpensive, it has been argued that cellular-relaying architectures can provide high bit-rate services at low infrastructure costs. This paper addresses the question of how inexpensive must a relay be, by converting the performance gains of the relaying architecture into cost constraints. The analysis is numerically exemplified on a study case where 95% downlink outdoor coverage must be provided in an urban environment. The relays are (randomly) placed on lamp-posts along streets. The transmission power, height and gain of the base station antennas, and the complexity of the relaying scheme are used to model the cost-performance trade-off. In this coverage study case, the relay to base station cost ratio must be at most 2 - 15%, depending on the above parameters' values. In the numerical examples, the relaying scheme type has much smaller impact on the cost ratio constraint than the base station antenna height and gain.

  • 9.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Coverage Costs with an Amplify-and-Forward Relaying Scheme2006Conference paper (Refereed)
    Abstract [en]

    The use of relaying technologies has previously beenproposed as lower cost alternatives to the traditional cellularsystems for providing wireless broadband access. In particular,parallel relaying uses combining diversity to improve the spectralefficiency on radio connections. This paper1 compares the infrastructurecosts of providing downlink coverage with and withoutrelays. The relays in the hybrid system are fixed, randomlydeployed, and are using a SIMO amplify-and-forward relayingscheme. The cost savings of using the relaying scheme are basedon empirical figures for the cost per unit/site. Numerical resultsshow that the use of relays improves the coverage, especially atlow SNR values, even with random relay deployment. Howeverthe coverage and cost savings are strongly dependent on thecharacteristics of the propagation environment and on the typesof units used. For instance, if the shadow fading from both therelays and the bases is uncorrelated, cost savings are obtainedonly if a base is at least 10 times more expensive than a relay.

  • 10.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT).
    Deployment cost efficiency in broadband delivery with fixed wireless relays2006Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    Although radio repeaters and wireless routers are commonly used, relaying techniques have received a lot of attention in academic publications the last decade. Most of the techniques proposed in the literature are based on relaying terminals. For instance groups of mobile terminals cooperate so as to jointly communicate with an access point, or to another group of mobiles in an (infrastructure-less) mobile ad-hoc network MANET. However, it has also been suggested that these techniques can be applied to hybrid cellular-relaying architecture with fixed relays and that this would reduce the infrastructure costs.

    The literature shows that the coverage or capacity of a cellular network is enhanced when using relays. A common assumption in these studies is that relays are very low cost, but little attention has been given to how cheap these relays need to be in order for the technical enhancements to translate into an economic gain. It is not obvious that the techniques proposed for mobile relaying are economically feasible when applied to fixed relays.

    This thesis examines the conditions under which large scale usage of fixed relays leads to lower infrastructure cost than in a purely cellular architecture, how large the benefits of these new techniques are, compared with existing repeater/router techniques, and how sensitive the results are to traditional network design parameters.

    The analysis is done by means of several study cases in which coverage should be provided for broadband services by building a network from scratch. The results are expressed in terms of how cheap a relay must be with respect to a base station's cost so that the hybrid infrastructure provides the desired service at a lower cost. If in practice this relative relay cost is much lower, then high economic gains are expected.

    None of the study cases considered yield substantial cost savings when using fixed relays on a large scale. When access points are placed as high as in a cellular network, the hybrid system is feasible only if the total relay cost is 3-20% of the total base station cost. When unplanned relay deployment is used, the impact of the antenna height and/or gain on the results is much greater than the particular type of amplify-and-forward relaying scheme. Planned deployment of a few relays should be used unless the cost of planning is 1-2 times larger than all the other relay costs. A proper trade-off between route-length and how tight the radio channel can be reused is essential for the feasibility of the hybrid system. The results confirm that the planned usage of few relays together with macro-like base stations is an efficient way of providing coverage. Analysis of other scenarios, such as the use of pico base stations for coverage, is left for further studies.

  • 11.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Planned Versus Ad-Hoc Deployment of Fixed Amplify-and-Forward Relays2006Conference paper (Refereed)
    Abstract [en]

    A previous study of the last-mile cost of a hybridcellular-relaying architecture [1], used for downlink coverage, hasshown that the ad-hoc (random) deployment of fixed relays maylead to some cost gains over the purely cellular system, but thatthese gains are strongly dependent on the unit costs. This paperstudies the benefits of using planned relay deployment, modeledby a pruning algorithm. As expected, the use of planned relaysenhances the feasibility of the hybrid architecture with respectto the cellular one. However, the ad-hoc deployment may stillbe feasible, in case the planning costs exceed the savings fromthe reduced number of units. For the hypothetical unit costsconsidered in the numerical examples, the ad-hoc deployment ispreferred if the base stations are of micro-type and the planningcosts exceed 5 keuro per km2.

  • 12.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Resource Allocation Schemes in Evaluating the Infrastructure Cost of a Wireless Multihop Architecture with Fixed Relays2005Conference paper (Refereed)
    Abstract [en]

    The downlink of a hybrid system with regenerative relaying (cellular extended by means of fixed wireless router) is studied in terms infrastructure costs. Using a static linear cost model, the feasibility of the hybrid system is analyzed by comparing the infrastructure cost of providing a predefined service level with a traditional single hop system and with a hybrid system, respectively. The analysis is performed with two resource allocation schemes: fixed and adaptive link rates. The same centralized STDMA scheme is used in both cases. The usage of adaptive rates reduces significantly the infrastructure cost of both the reference and the hybrid system. However, the hybrid system becomes feasible when the cost of a relay is 6 to 9% the cost of a base station, no matter which of the two resource allocation scheme is used.

  • 13.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Roll-out Decisions in a Multihop Cellular System with Fixed Relays2005Conference paper (Refereed)
    Abstract [en]

    The infrastructure costs of a hybrid multihop cellular has previously been analyzed by assuming fixed traffic loads. In reality the traffic load in a commercial system gradually increases and therewith the network must be upgraded. The timing and the type of upgrade may have important impact on the overall infrastructure cost. A first step in analyzing the costs of a hybrid network roll-out is taken in this paper. It is assumed that a wireless relay can be turned into an access point by connecting it to a wired transport network. A criterion is introduced for deciding whether to deploy a new relay or turn an old one into an access point, based on the estimated capacity increase and on the present value of the additional costs associated with each upgrade type. The decision is taken as a single-action event at a given time, i.e. ignoring the opportunities created or missed by the decision. It also assumes that the equipment is worth nothing at the end of the operational phase. Numerical examples in a simple deployment scenario show that it is worth deploying relays for up to three hops, at the beginning of the operation period, if the units are of pico-base station type. Relays are always turned into access points toward the end of the operation period.

  • 14.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    Studies on the Viability of Cellular Multihop Networks with Fixed Relays2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The use of low cost fixed wireless relays has been proposed as a way to deploy high data-rate networks at an affordable cost. During the last decade, significant academic and industrial research has been dedicated to relays. Protocol architectures for cellular-relaying networks are currently considered for standardization as part of both IEEE 802.16 and 3GPP. Various relaying techniques have successfully been commercialized over the years. This dissertation concentrates on the particular case of large scale use of low cost relays, for which focus is put on signal processing and radio resource allocation, rather than on antenna and radio frequency (RF) design, or on network planning. A key question is how low relay cost is low enough for a relaying architecture to be viable from an economic point of view? We develop a framework for evaluating the viability of relaying solutions. The framework is based on a comparison between the relaying architectures and traditional single-hop cellular architectures. This comparative analysis is done from an operator perspective, and is formulated as a network-dimensioning problem. The associated investment decisions are based on financial measures (cost or profit) and taken under technical constraints (throughput, coverage, etc.).First, we consider a large number of traditional dimensioning scenarios, in which the radio network is design for a predefined traffic demand and target quality of service level. We show that the use of low cost relays can indeed be viable, but that the cost savings vary strongly from case to case and often are only modest. Due to the half-duplex nature of the low cost relays, these relays are best suited for providing coverage to guaranteed data-rates, at low end-to-end spectral efficiency, and in environments with strong shadow fading. The type of environment and the placement of relays are more important than the specific protocols and algorithms used in the network. Therefore, traditional network planning remains an essential and challenging task, which is unlikely to be replaced by large-scale (unplanned) use of relays.Second, we suggest a new direction of research in which the viability of relays is judged considering the entire life cycle of a radio network. We give several examples in which the temporary use of relays is economically viable, especially if the service uptake is slow or the uncertainty about the future demand is high. This is particularly relevant if the last-mile cost of a network is dominated by the backhaul transmission cost, and if relaying is implemented as a feature of an access point, rather than as a new device type.

  • 15.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Performance analysis of an amplify and forward relaying scheme with pre-coding2007In: 2007 IEEE 18TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-9, IEEE , 2007, p. 2834-2838Conference paper (Refereed)
    Abstract [en]

    Cooperative diversity can combat fading on multipath channels by exploiting space diversity available through cooperative relays. Half-duplex relaying is quite simple to implement but it is useful only when the direct link is weak. By allowing the source to transmit continuously, full-rate relay channels can be obtained. However, the performance of such a full-rate scheme is still limited by the direct link. In this paper1 we consider pre-coding at the transmitter as a way of improving the performance of full-rate relay channels. The obtained results show that, with a proper selection of the pre-coding parameters, better system capacity can be obtained.

  • 16.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Hultell, Johan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Nilson, Mats
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Techno-economical viability of deployment strategies for cellular-relaying networks2008In: 2008 IEEE 67TH VEHICULAR TECHNOLOGY CONFERENCE-SPRING: Vols 1-7, 2008, p. 2259-2263Conference paper (Refereed)
    Abstract [en]

    The ability of an operator to respond to changes in demand by incrementally deploying additional network infrastructure is essential. This paper(1) presents a method for evaluating and comparing the economic viability of incremental deployment strategies given a limited initial investment budget. Any strategy is seen as a sequence of deployment decisions. The time-dynamic relation between service quality and demand is taken into account via the limited investment budget (cash How analysis), while the focus is maintained on the technical properties of the network. As an example, the economic viability of a 1D cellular-relaying network is analyzed under greedy deployment strategies. In order for the cellular-relaying solution to be viable, we show that the maximum allowed relay cost decreases with the investment budget.

  • 17.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    A Joint Routing-MAC Model for Cellular-Relaying Networks2008In: 2008 IEEE 19TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, NEW YORK: IEEE , 2008, p. 1214-1219Conference paper (Refereed)
    Abstract [en]

    We present an iterative joint scheduling-routing algorithm for characterizing the long-term performance of a cellular-relaying network. The physical layer model is based on ideal rate adaptation, fixed transmission power, and average interference. At the MAC layer, time-shares of a common channel are allocated to links in a CSMA/CA-like fashion. At the transport layer, one or more parallel routes can transfer the data flow from a source to the destination, and the average end-user rates are adjusted so as to maximize a global utility function. The general problem of allocating time-shares and selecting link rates is nonconvex. We propose an iterative algorithm and a novel approximation for the physical layer so as to obtain a convex formulation at each iteration step. If only one route is available per source, the problem admits a convex equivalent formulation and the iterative algorithm converges to the global optimum. If more routes per source are available, the problem remains nonconvex. However we show in a simple tractable example that the joint formulation yields sum-log-utility values comparable to the results obtained through exhaustive search of all possible route combinations.

  • 18.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Cellular-Relaying Network Dimensioning with Cross-Layer Resource Allocation2008In: 2008 IEEE 19TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, NEW YORK: IEEE , 2008, p. 1236-1240Conference paper (Refereed)
    Abstract [en]

    The enhancement of cellular networks with relaying technologies is expected to bring significant techno-economic benefits, but proper allocation of resources may be a challenging task. This paper addresses the question whether cross-layer optimization is essential for obtaining the expected relaying benefits. We present a network dimensioning approach based on joint routing and radio resource allocation. We consider a macro-cellular scenario with a max-min user-rate objective. If a single route per source is fixed, rates and time-shares can be optimally allocated to each link. In a simple macro-cellular propagation environment, the relays must cost at most 10-25% of a base station cost, if the network is deployed at once. The results are only slightly better when the routing is included in the joint resource allocation.

  • 19.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Kim, Dongwoo
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Cross-Layer Resource Allocation Model for Cellular-Relaying Network Performance Evaluation2011In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 6, p. 2765-2776Article in journal (Refereed)
    Abstract [en]

    The enhancement of cellular networks with relaying technologies is expected to bring significant technoeconomic benefits at the expense of more complex resource allocation. Suitable models for solving network dimensioning problems in cellular-relaying networks must handle radio resource allocation among hundreds of links and tackle interactions between networking layers. For this purpose, we propose a novel cross-layer resource allocation model based on average interference and ideal rate adaptation for the physical layer (PHY), time shares for the medium access layer, and fluid flows for the transport and network layers. We formulate a centralized social welfare maximization problem. When the routes are selected with an a priori algorithm, we show that the resource allocation problem admits an equivalent convex formulation. We show a numerical example for how to use the proposed framework for configuring the backhaul link in a practical relaying network. The overall problem of selecting routes and allocating time shares and link rates is nonconvex. We propose an iterative suboptimal algorithm to solve the problem based on a novel approximation of PHY. We state and prove several convergence properties of the algorithm and show that it typically outperforms routing based on signal-to-noise ratio only.

  • 20.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Implications of fairness criteria on the techno-economic viability of relaying networks2009In: 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, 2009, p. 3050-3054Conference paper (Refereed)
    Abstract [en]

    The introduction of relaying techniques into cellular networks is expected to reduce the total infrastructure cost, especially when coverage extension is sought. With the advent of networks such as LTE, guaranteeing high data-rate coverage may become a challenge even for incumbent operators which nowadays provide full coverage for voice service. However it is not straightforward that operators will be able (or want) to guarantee coverage for the high data-rates. In this paper we study how the techno-economic viability of the relaying solution depends on the type of service to be provided by the operator. We exemplify the trade off between coverage and system throughput with two fairness criteria: perfect fairness (coverage guarantee) and proportional fairness. We show that relays provide advantages when the operator is interested in providing bit-rate/QoS guarantees. When maximizing the system throughput or cell capacity, relays are of less value.

  • 21.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    Incremental Deployment with Self-backhauling Base Stations in Urban Environment2009In: 2009 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOPS, NEW YORK: IEEE , 2009, p. 541-545Conference paper (Refereed)
    Abstract [en]

    High capacity mobile broadband access requires a dense infrastructure of base stations. The costs associated with the backhaul transmission for these base stations is often a significant part of the total cost of the access network. It has been proposed to use part of the available spectrum to route data between base stations, so-called in-band relaying or self-backhauling. Although self-backhauling may result in a lower total system capacity, we will in this paper show examples where temporary use of in-band relaying postpones investments in fixed backhaul connections. This reduces the total (life-time) cost of the access network. In our incremental strategy example the total cost savings are in the order of 5 to 10%, depending on the relation between the additional equipment cost and the cost of leasing the fixed backhaul. Self-backhauling is not worth implementing when the entire network capacity needs to be achieved up-front, but the savings are significant when service uptake is slow or difficult to predict. The discount rate used in the investment analysis has only a minor impact on the results.

  • 22. Wang, Y.
    et al.
    Wei, Xiaoyu
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Timus, Bogdan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Sankar, R.
    Morgera, S.
    Feasibility study of pico cellular-relaying system in urban outdoor environment2011In: 2011 IEEE 12th Annual Wireless and Microwave Technology Conference, WAMICON, 2011Conference paper (Refereed)
    Abstract [en]

    Heterogeneous networks, in particular cellular-relaying networks, have the potential to provide high data-rate services at low infrastructure costs. Macro and micro base stations have traditionally been used to provide coverage and capacity, respectively. In this paper, we analyze a new approach in which coverage is provided by means of inband relays. We show that compared with a traditional network based on macro base stations, a good outdoor coverage for a target data rate could be provided in a more cost efficient way by deploying a network based on pico base stations and relays. However, this is valid only for low data-rate because part of the spectrum is allocated to the backhaul and therefore the capacity of cellular-relaying networks is typically limited. Moreover, this break-even point depends on how the networks are deployed.

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