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Future Cooperative Networks


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Future Cooperative Networks

  1. 1. Evolution of Heterogeneous Wireless Networks
  2. 2. From 1G to 4G
  3. 3. Evolution  1G Analog Cellular systems ○ AMPS  2G Digital Cellular systems ○ GSM, CDMA, CDMAone, TDMA  2.5G Voice and Data transmission ○ GPRS, HSCDS, TDMA, CDMAone  3G Broadband digital ○ W-CDMA, EDGE
  4. 4. Wireless Networks  Centralized wireless networks:  nodes communicate with a base station or an access point over single hop links  Wireless ad hoc networks:  End-to-end communication is carried over multiple hops realized through intermediate nodes  Applications:  wireless mesh networks  wireless sensor networks  mobile networks  Attributes:  minimal configuration requirements  quick deployment  decentralized operation
  5. 5. Wireless Networks  Limited performance: 1. The end-to-end path consists of multiple concatenated unicast links along specified nodes on a predetermined path. (errors due to channel impairments caused by fading and mobility) 2. Failure of a link can make entire end-to-end path inoperable, requiring route rediscovery and maintenance procedures 3. In case of harsh environmental conditions, the route discovery phase needs repetition causing messaging burden, thereby leading to wasted network bandwidth and degraded throughput 4. Routing messages are delivered by contending for the available medium 5. Contention avoidance and resolution mechanisms also steal from the network bandwidth that could otherwise be used for data communication 6. As the network size is increased, the message overhead of routing strategies is also increased, resulting in further degradation in throughput and delayed performance
  6. 6. Cooperative Networks  If each user devotes some of its resources to relaying the transmissions it hears from other users as well as to sending its own message, message is received with higher reliability because of multiple propagation paths  Cooperating users form a "virtual" antenna array, from which there is a substantial spatial diversity benefit.  Simple relaying schemes yield full spatial diversity: each user's message experiences performance as if it were sent from a physical antenna array of the same size.  Result in novel and efficient distributed space- time codes for networks  Equally applicable to cellular and ad-hoc architectures  Slight violation of the traditional abstraction rules that impose a separation of the physical, link, and network layers.
  7. 7. Cooperative Wireless Networking Architecture Cooperative Network Macro Cooperative Network Micro Cooperative Network  Infrastructure based division  Macro – Cooperative Diversity  Micro – Cellular Controlled point to point (P2P) network
  8. 8. Macro Cooperative Network Architecture  Relay terminal can be fixed and is installed by network operator  Relay terminal can be a mobile terminal  For mobile relay terminal, packet forwarding fairness and incentive issues need to be taken into account  Transmission between relay terminal and mobile terminal can be implemented by  relays’ cooperative repetition  simultaneous transmission with space- time coding  selection and dynamic relay
  9. 9.  Composed of cellular mobile network and nomadic wireless network  Mobile terminal must be multi- modality terminal – capable of communication to both cellular link with base station and short-range link with peer terminals  Exchanged information between mobile terminals is not simple packets forwarding or relaying  What, how and when to exchange the information between/among mobile terminals depends on  the targeted cooperative scenario  the designed cooperative mechanism Micro Cooperative Network Architecture
  10. 10. Micro Cooperative Scenario Matrix
  11. 11.  Unicast Transport Unicast Service (UU):  mobile ter-minals have individual unicast services  services are transmitted by unicast transports  Example:  Cooperative header exchange for robust header compression in VoIP  Exchanging of compressed packet header of voice packet can help partner to immediately recover the decoding reference when one voice packet is lost Micro Cooperative Scenario Matrix
  12. 12.  Unicast Transport Multicast Service (UM)  Mobile terminals have multicast service  Service is transported by unicast link to different terminals  Examples  Multiple De-scription Coding (MDC)/Multiple Layer Coding (MLC) video services or Peer-to-Peer services fit this scenario Micro Cooperative Scenario Matrix
  13. 13.  Multicast Transport ”Unicast” Services (UM):  mobile terminals have individual varying services  These services are transmitted in a multicast/broadcast fashion  Example  DVB-H services are multicasted/ broadcasted over parallel elementary streams Micro Cooperative Scenario Matrix
  14. 14.  Multicast Transport Multicast Service (MM):  the mobile terminals are interested in the same multicast service  this service is transmitted by multicast  Example  Reliable cooperative local retransmission Micro Cooperative Scenario Matrix
  15. 15. Future Cooperative Networks  Evolving views of future heterogenuous wireless networks  Increasing need for  Density of nodes  Data throughput  Limiting factors  Available freq. spectrum  Available bandwidth  Room for improvement  Spectral efficiency  Link reliability  Aim – high data rates
  16. 16. Future Cooperative Networks  Cooperation between base stations and possibly also between mobile user stations in micro- and femtocells  Multinode cooperation with the use of additional nodes acting as relays in macrocells as well as in micro- and femtocells  Relaying concepts in wireless home networks
  17. 17. The End Q&A?