future cooperative networks

Future Cooperative NetworksEvolution of Heterogeneous Wireless Networks

Evolution and Background

From 1G to 4G

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

Prevalent Wireless Networks

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

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

Cooperative Networks

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.

Cooperative Networks Architecture

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

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

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

Micro Cooperative Scenario Matrix

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


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


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


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


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


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

The EndQ&A?

future cooperative networks

Engineering