1. Evolution of Heterogeneous Wireless Networks

2. From 1G to 4G

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

5. 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

6. 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

8. 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.

10. 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

11. 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

12.  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

13. Micro Cooperative Scenario
Matrix

14.  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

15.  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

16.  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

17.  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

19. 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

20. 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

21. The End
Q&A?