11-10-2012, 10:29 AM
3G wireless systems: UMTS
[attachment=36005]
UMTS Service aspects and Service Capabilities
Radio operating environments
indoor
outdoor to indoor and pedestrian
vehicular and fixed outdoor
(satellite)
Data rates
up to at least 144 kbps in vehicular environment with full mobility
up to at least 384 kbps in suburban outdoor and outdoor to indoor environments with medium mobility
up to 2 Mbps with low mobility in pico cells and indoor
Packet and circuit oriented, symmetric and asymmetric services
CDMA & spread spectrum
CDMA = Code Division Multiple Access
Spread spectrum is a characteristic of a signal; the signal is not necessarily intended for a multiple access of a common medium (e.g. anti-jamming)
Signals used in CDMA are usually spread spectrum signals
There are many types of spread spectrum, e.g.
Direct Sequence this is the only one we consider here
Frequency hopping
Soft handoff (hand-over)
The two Base Stations use different scrambling codes
Soft handoff exploits macro-diversity
Softer handoff: between two sector of the same BS
Active Set: set of BS connected to a mobile
Candidate Set: set of BS whose signals has been detected by the mobile but not currently connected
Power control & soft handoff
Power control minimise intra-cell interference
Inter-cell interference minimisation is achieved through soft handoff and careful selection of the BS involved in it
Codes planning
Different Base Stations must have different scrambling codes
e.g. to permit to the mobile to distinguish between signals coming from different BS
“Different” scrambling codes
“completely” different scrambling codes
scrambling codes made by shifting a unique mother code
Synchronous & asynchronous networks
Synchronous network: all BS are tightly synchronised (e.g. through GPS)
Asynchronous network: BS are not supposed to be synchronised
In synchronous networks we can use a set o scrambling codes made from shifts of a unique mother code
Logical channels
Control channels (C-plane information)
Synchronisation Control CHannel (DL)
Broadcast Control CHannel (DL)
Paging Control CHannel (DL)
Common Control CHannel (UL&DL)
Dedicated Control CHannel (UL&DL)
Shared Control CHannel
ODMA Dedicated Control CHannel
[attachment=36005]
UMTS Service aspects and Service Capabilities
Radio operating environments
indoor
outdoor to indoor and pedestrian
vehicular and fixed outdoor
(satellite)
Data rates
up to at least 144 kbps in vehicular environment with full mobility
up to at least 384 kbps in suburban outdoor and outdoor to indoor environments with medium mobility
up to 2 Mbps with low mobility in pico cells and indoor
Packet and circuit oriented, symmetric and asymmetric services
CDMA & spread spectrum
CDMA = Code Division Multiple Access
Spread spectrum is a characteristic of a signal; the signal is not necessarily intended for a multiple access of a common medium (e.g. anti-jamming)
Signals used in CDMA are usually spread spectrum signals
There are many types of spread spectrum, e.g.
Direct Sequence this is the only one we consider here
Frequency hopping
Soft handoff (hand-over)
The two Base Stations use different scrambling codes
Soft handoff exploits macro-diversity
Softer handoff: between two sector of the same BS
Active Set: set of BS connected to a mobile
Candidate Set: set of BS whose signals has been detected by the mobile but not currently connected
Power control & soft handoff
Power control minimise intra-cell interference
Inter-cell interference minimisation is achieved through soft handoff and careful selection of the BS involved in it
Codes planning
Different Base Stations must have different scrambling codes
e.g. to permit to the mobile to distinguish between signals coming from different BS
“Different” scrambling codes
“completely” different scrambling codes
scrambling codes made by shifting a unique mother code
Synchronous & asynchronous networks
Synchronous network: all BS are tightly synchronised (e.g. through GPS)
Asynchronous network: BS are not supposed to be synchronised
In synchronous networks we can use a set o scrambling codes made from shifts of a unique mother code
Logical channels
Control channels (C-plane information)
Synchronisation Control CHannel (DL)
Broadcast Control CHannel (DL)
Paging Control CHannel (DL)
Common Control CHannel (UL&DL)
Dedicated Control CHannel (UL&DL)
Shared Control CHannel
ODMA Dedicated Control CHannel