01-02-2013, 02:19 PM
Wireless communication
Wireless communication.pptx (Size: 369.67 KB / Downloads: 32)
Is there a future for wireless?Some history
Ancient Systems: Smoke Signals, Carrier Pigeons, …
Many sophisticated military radio systems were developed during and after WW2
Cellular has enjoyed exponential growth since 1988, with almost 1 billion users worldwide today
Ignited the recent wireless revolution
Growth rate tapering off
3G (voice+data) roll-out disappointing
Glimmers of Hope
Internet and laptop use exploding
2G/3G wireless LANs growing rapidly
Low rate data demand is high
Military and security needs require wireless
Emerging interdisciplinary applications
Design Challenges
Wireless channels are a difficult and capacity-limited broadcast communications medium
Traffic patterns, user locations, and network conditions are constantly changing
Applications are heterogeneous with hard constraints that must be met by the network
Energy and delay constraints change design principles across all layers of the protocol stack
3G Cellular Design: Voice and Data
Data is bursty, whereas voice is continuous
Typically require different access and routing strategies
3G “widens the data pipe”:
384 Kbps.
Standard based on wideband CDMA
Packet-based switching for both voice and data
3G cellular struggling in Europe and Asia
Evolution of existing systems (2.5G,2.6798G):
GSM+EDGE
IS-95(CDMA)+HDR
100 Kbps may be enough
What is beyond 3G?
Bluetooth
Cable replacement RF technology (low cost)
Short range (10m, extendable to 100m)
2.4 GHz band (crowded)
1 Data (700 Kbps) and 3 voice channels
Widely supported by telecommunications, PC, and consumer electronics companies
Few applications beyond cable replacement