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Capacity and Range Enhancement Techniques for the Third Generation Mobile Communications and Beyond (Ref. No. 2000/003), IEE Colloquium on

Date 2000

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Displaying Results 1 - 10 of 10
  • Space-time estimation techniques for UTRA system

    Page(s): 6/1 - 6/7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    This paper investigates the space-time channel estimation techniques in a multiple-access communication receiver system that receives coded digital data modulated using DS-CDMA, with an antenna array in a multipath propagation environment. A spatial and temporal channel model has been implemented, which is built upon the understanding of multipath fading and Doppler spread with merging time delay spread, direction-of-arrival and adaptive antenna array geometry. A receiver structure based on space-time processing has also been implemented, i.e. a reverse link, single-user (SU) with single antenna input (SI) at mobile and multiple antenna output (MO) at the base (SU-SIMO). A reverse link, multiuser (MU) SIMO has been presented as well. This paper also provides an overview of various methods available for estimation of DOA of a radio signal using an antenna array. Joint angle and delay estimation (JADE) combined with MUSIC is proposed as the main candidate for estimating the channel profile. For this purpose we present the performance of MUSIC as used in UTRA system View full abstract»

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  • DOA estimation using a relaxation based method

    Page(s): 2/1 - 2/5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    A modified relaxation based method is employed to minimise the maximum likelihood function in the estimation of the DOA of signals impinging on an antenna array. The method is suitable for estimating DOAs of coherent signals and in the case where the number of snapshots is limited. Simulation results are used to demonstrate the performance of the relaxation-based method relative to that of other methods View full abstract»

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  • Space-time coding in the third generation and beyond

    Page(s): 7/1 - 7/8
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    We consider space-time coding and other techniques which have been developed to take advantage of the substantial capacity increases which are available in multi-antenna, or MIMO (multiple-in, multiple-out) radio channels. We address the question of how and to what extent these techniques may be exploited in third generation mobile systems based on standards such as UMTS. We consider both the dependence of the capacity on the radio environment, and the requirements of signal design for these channels. We show that the standard may be adapted to provide both capacity gains and diversity improvements, but care must be taken to ensure backward compatibility with handsets not designed for these signals. Multi-user detection is also important to provide a good signal to noise ratio View full abstract»

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  • SFDMA-spatial focus division multiple access

    Page(s): 3/1 - 3/7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The concept of spatial focus division multiple access (SFDMA) is presented. SFDMA intends to increase capacity by exploiting diversity as well as reducing interference. Adaptive antennas are employed to focus the power of more than one base station simultaneously towards the mobile station's position. Signals focused towards the mobile station are divided by code division multiple access. The availability of space diversity facilitates the mitigation of Rayleigh fading as well as of log-normal fading caused by shadowing. As signals come from various base stations they can be exploited by navigational processing in order to obtain a position estimation as an alternative to ranging signals of global navigation satellite systems View full abstract»

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  • Adaptive cell sizing in cellular networks

    Page(s): 4/1 - 4/5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    This paper investigates the potential capacity improvements made possible through the use of dynamic cell sizing in a cellular network. The purpose of dynamic cell sizing is to reduce cell radii and thus enable in-cell users to increase their transmit powers. The use of higher transmit powers suppresses intercell interference and leads to an overall increase in capacity. This paper discusses the degree of capacity enhancement that can be achieved in this manner. The analysis indicates that the capacity of a single cell can be increased by as much as 38%. However, under uniform traffic conditions, this results in a ratio of supported-to-offered traffic of just 0.2, which is clearly unsatisfactory. Dynamic cell sizing performs significantly better in hot-spot conditions, where the in-cell traffic follows a normal distribution with the highest density close to a central basestation. The ratio of supported-to-offered traffic under these conditions was found to rise to a more acceptable 0.7-0.8 depending on the traffic standard deviation View full abstract»

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  • Planning and optimisation of smart antenna base stations in 3G networks

    Page(s): 1/1 - 1/7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    In the initial UMTS infrastructure deployment, sector antenna-equipped base sites will predominate. It is likely that the first switched-beam antenna products will be available in 2001/2, when build out is underway. Operators may choose to replace sector antennas for switched beam units on some sites where traffic demand is expected to be very high. The `smart sectorisation' of a site's coverage area afforded by this type of smart antenna product can be used to enhance capacity by reducing overall interference levels. This is a kind of SFIR (spatial filtering for interference reduction). Early in UMTS Phase 1, fully adaptive antennas will become available to network operators. This class of smart antenna offers enhanced SFIR capability relative to that of the switched beam units, and additionally offers the possibility of single-cell frequency reuse, SDMA (space division multiple access). In SDMA, the network capacity is increased via a double benefit of optimum/switched beamforming. Firstly, overall interference levels are reduced as a result of more closely targeting power toward the terminal of interest. Secondly, optimal minimisation of unwanted power from non-served terminals allows scarce short channelisation codes to be reused by high data-rate users within the coverage area of the same cell. Planning tools for 3G networks will harness the potential of these revolutionary changes in network infrastructure, and additionally will alleviate the complexity for the radio planner of handling a multiservice, multi-bearer environment View full abstract»

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  • Space-time coding for capacity enhancement in future-generation wireless communications networks

    Page(s): 8/1 - 811
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    We present a simple yet novel space-time coding (STC) approach, based on a logical extension of simple convolutional codes. We compare this STC scheme with known transmission techniques, including space-time transmit diversity (STTD) and BLAST, in terms of code construction and performance. We present simulation results of actual performance, and discuss the reasons for, and implications of, the performance trends observed View full abstract»

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  • Considerations for UMTS capacity and range estimation

    Page(s): 5/1 - 5/6
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    In this paper, example uplink and downlink capacity and range estimation methods have been outlined. These have been limited to the single service case where the modem performance, multipath structure, environmental conditions and service rate are common to all users in the network. It has been found that uplink capacity estimation is primarily a function of modem performance and the F-factor. This is due to the dominance of other user noise over the thermal noise, even in lightly loaded cells, as well as the variability of the in-cell and out-of-cell noise (the F-factor). Simplifications to the downlink numerical modelling have been shown using fixed RAKE finger characteristics. These simplifications assume that the average channel conditions do not change with position, time or when the subscriber unit is in soft-handover. We have also considered the consequences of the simplified link-budget and user to interference margin mapping in the context of estimating capacity and range for a homogenous network. Homogeneity does not describe realistic network topologies; however, the generic case does give some indication of UMTS capabilities. Coupled with a numerical modelling technique, the methods outlined in this paper can help dimension the air-interface network for UMTS View full abstract»

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  • Fast linear multi-user detector for DS-CDMA systems

    Page(s): 10/1 - 10/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    This paper reviews the family of linear multi-user detectors and compares them in terms of complexity and performance. The complexity of such detectors due to matrix inversion operation is also discussed. An approximate method for computing the inverse of correlation matrix based on series expansion is presented. This method is less complex and easy to implement. The problem is examined and a new and looser condition for convergence of the series is derived. This method has the property of fast convergence compared to other methods reported in the literature. The paper finally gives the simulation results View full abstract»

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  • Intelligent relaying for future personal communication systems

    Page(s): 9/1 - 9/5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    This paper highlights the key benefits of using intelligent relaying (IR) for future personal communication systems. IR is a technique that incorporates direct mobile to mobile communication, allowing end-to-end connectivity in a network to be implemented via a number of short hops. A mobile can in theory reach any destination by transmitting only as far as its closest neighbour, bringing potential benefits such as an overall reduction in transmit power, and the possibility of increased capacity. In addition, the self-organising nature of the network may reduce the need for network planning and basestation infrastructure. Issues investigated in this paper include the definition of a suitable path loss model for use between mobile stations. Simulations using this path loss model in a test environment show that average total power savings of 21 dB are possible, compared with a conventional microcell not using relaying. It is also shown that area coverage in the test environment can be increased by 70%, due to the possibility of using relaying to extend services into shadowed areas View full abstract»

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