The handling of intercell interference at the cell border area is a strong demand in future communication systems to guarantee efficient use of the available bandwidth. Therefore, this paper focuses ...on the application of iterative intercell interference cancellation schemes in cellular multicarrier code division multiple access (MC-CDMA) systems at the receiver side for the downlink. First, the influence of the interfering base stations to the total intercell interference is investigated. Then, different concepts for intercell interference cancellation are described and investigated for scenarios with several interfering cells. The first approach is based on the use of the hard decision of the demodulator to reconstruct the received signals. This does not require the higher amount of complexity compared to the second approach which is based on the use of the more reliable soft values from the decoding process. Furthermore, the extrinsic information as a reliability measure of this soft iterative cancellation process is investigated in more detail based on the geographical position of the mobile terminal. Both approaches show significant performance gains in the severe cell border area. With the soft intercell interference cancellation scheme, it is possible to reach the single-user bound. Therefore, the intercell interference can be almost eliminated.
Positioning Based on Factor Graphs Mensing, Christian; Plass, Simon
EURASIP journal on advances in signal processing,
01/2007, Letnik:
2007, Številka:
1
Journal Article
Recenzirano
Odprti dostop
This paper covers location determination in wireless cellular networks based on time difference of arrival (TDoA) measurements in a factor graphs framework. The resulting nonlinear estimation problem ...of the localization process for the mobile station cannot be solved analytically. The well-known iterative Gauss-Newton method as standard solution fails to converge for certain geometric constellations and bad initial values, and thus, it is not suitable for a general solution in cellular networks. Therefore, we propose a TDoA positioning algorithm based on factor graphs. Simulation results in terms of root-mean-square errors and cumulative density functions show that this approach achieves very accurate positioning estimates by moderate computational complexity.
This work presents an overview of the radio interface of VHF Data Exchange System (VDES), which is currently on its way to become an ITU standard supported by International Association of Marine Aids ...to Navigation and Lighthouse Authorities. VDES includes the already existing collision avoidance tracking system Automatic Identification System and the messaging system Application Specific Messages. Additionally, a new third component for digital maritime communications of any kind, named VHF Data Exchange is included. On the one hand, there is a traditional terrestrial component, on the other hand, a satellite communication link is also envisioned partly by the same spectrum usage. In this article, focus is given towards the technical design aspects and challenges of this hybrid communications transmission scheme.
There are well-founded concerns that current air transportation systems will not be able to cope with their expected growth. Current processes, procedures and technologies in aeronautical ...communications do not provide the flexibility needed to meet the growing demands. Aeronautical communications is seen as a major bottleneck stressing capacity limits in air transportation. Ongoing research projects are developing the fundamental methods, concepts and technologies for future aeronautical communications that are required to enable higher capacities in air transportation. The aim of this book is to edit the ensemble of newest contributions and research results in the field of future aeronautical communications. The book gives the readers the opportunity to deepen and broaden their knowledge of this field. Today's and tomorrow's problems / methods in the field of aeronautical communications are treated: current trends are identified; IPv6 aeronautical network aspect are covered; challenges for the satellite component are illustrated; AeroMACS and LDACS as future data links are investigated and visions for aeronautical communications are formulated.
Positioning Based on Factor Graphs Mensing, Christian; Plass, Simon
EURASIP journal on advances in signal processing,
2007-Jun-26, Letnik:
2007, Številka:
1
Journal Article
Recenzirano
Odprti dostop
: This paper covers location determination in wireless cellular networks based on time difference of arrival (TDoA) measurements in a factor graphs framework. The resulting nonlinear estimation ...problem of the localization process for the mobile station cannot be solved analytically. The well-known iterative Gauss-Newton method as standard solution fails to converge for certain geometric constellations and bad initial values, and thus, it is not suitable for a general solution in cellular networks. Therefore, we propose a TDoA positioning algorithm based on factor graphs. Simulation results in terms of root-mean-square errors and cumulative density functions show that this approach achieves very accurate positioning estimates by moderate computational complexity.
The Aeronautical Mobile Airport Communications System (AeroMACS) has been developed for future high-rate, secure, and safety enhancing airport communications in the C-band. Although initially ...designed for ground applications, the relatively large radio coverage area of AeroMACS suggests its potential extension to new operative scenarios wherein a data link is established between the control tower and the aircraft even when the latter is not in contact with the airport surface. An examination is needed for these new applications concerning channel properties, synchronization aspects, and general performance behaviors. In this paper, the possibility of using AeroMACS during the approach, landing, and takeoff phases of an aircraft flight is investigated. After deriving the channel parameters for the new application scenarios, the synchronization and channel estimation algorithms are presented and the overall error rate performance is assessed by means of computer simulations. Our results indicate that AeroMACS is able to cope with the new operational phases and its use can be extended beyond airport surface applications.
We address the problems at the most critical area in a cellular multicarrier code division multiple access (MC-CDMA) network, namely, the cell border. At a mobile terminal the diversity can be ...increased by using transmit diversity techniques such as cyclic delay diversity (CDD) and space-time coding like Alamouti. We transfer these transmit diversity techniques to a cellular environment. Therefore, the performance is enhanced at the cell border, intercellular interference is avoided, and soft handover procedures are simplified all together. By this, macrodiversity concepts are exchanged by transmit diversity concepts. These concepts also shift parts of the complexity from the mobile terminal to smart base stations.
: We address the problems at the most critical area in a cellular multicarrier code division multiple access (MC-CDMA) network, namely, the cell border. At a mobile terminal the diversity can be ...increased by using transmit diversity techniques such as cyclic delay diversity (CDD) and space-time coding like Alamouti. We transfer these transmit diversity techniques to a cellular environment. Therefore, the performance is enhanced at the cell border, intercellular interference is avoided, and soft handover procedures are simplified all together. By this, macrodiversity concepts are exchanged by transmit diversity concepts. These concepts also shift parts of the complexity from the mobile terminal to smart base stations.
PDF
