1. Telecom Consultants International TETRA BSG 15/2/00 - 1 Traffic Capacity issues facing the TETRA Application Developer Richard Dewey 15 February 2000

2. Telecom Consultants International TETRA BSG 15/2/00 - 2 Outline of presentation TETRA tele and bearer services Mixed voice + data traffic profiles Insight from simple air interface model Typical traffic performance results Summary Telecom Consultants International

3. TETRA BSG 15/2/00 - 3 Clear Speech or Encrypted Speech INDIVIDUAL CALL (POINT TO POINT) BROADCAST (POINT TO MULTIPOINT ONE WAY) GROUP CALL (POINT TO MULTIPOINT) ACKNOWLEDGED GROUP CALL (POINT TO MULTIPOINT) Tele Services Supported by TETRA

4. Telecom Consultants International TETRA BSG 15/2/00 - 4 Bearer Services Supported by TETRA Circuit mode unprotected data: 7.2, 14.4, 21.6, 28.8 kbits/sec Circuit mode low protected data: 4.8, 9.6, 14.4, 19.2 kbits/sec Circuit mode high protected data: 2.4, 4.8, 7.2, 9.6 kbits/sec Packet connection oriented data Packet connectionless data Short Data Services - 65535 Status messages (half reserved) user defined data types –type 1: 16 bits data –type 2: 32 bits data –type 3: 64 bits data –type 4: up to 2047 bits data

5. Telecom Consultants International TETRA BSG 15/2/00 - 5 Traffic performance criteria Voice calls –T95 average, T95 maximum –access throughput, blocking probability –system throughput Data calls –intrinsic delay –throughput

6. Telecom Consultants International TETRA BSG 15/2/00 - 6 Mixed voice + data traffic profiles Mixture of individual and group calls? Mixture of voice and data? Length of voice calls? Size of data messages: packet and SDS1234 Priorities for different voice calls?

7. Telecom Consultants International TETRA BSG 15/2/00 - 7 Simple model of air interface Control channel –grants access –allocates traffic chans –carries packet data Traffic channels –carry circuit mode voice + data SERVERS Queue server 1234 Queues Access Control Data

8. Telecom Consultants International TETRA BSG 15/2/00 - 8 Control mechanisms for air interface Access priority to get in to the system. Queue priority gets in to the favoured Q. Pre-emptive priority removes low priority active user to gain immediate service. SERVERS Queue server 1234 Queues Access Control Data

9. Telecom Consultants International TETRA BSG 15/2/00 - 9 Performance limiting factors Control channel loading –access on the uplink –capacity on the downlink Traffic channel loading –availability of channels

10. Telecom Consultants International TETRA BSG 15/2/00 - 10 Monte Carlo simulation Define traffic load –subscriber characteristics (individuals, groups, dispatchers, location) –traffic generated by each user Generate traffic load Run air interface protocol simulation Analyse traffic runs Plot results

11. Telecom Consultants International TETRA BSG 15/2/00 - 11 Results

12. Telecom Consultants International TETRA BSG 15/2/00 - 12 Summary Realistic traffic results only by full simulation. Will take account of –voice + data traffic mix –voice priority mix –mix of data bearer services (SDS1234 and status). HOWEVER priority between voice and data is “an implementation issue”. Supplementary or extended control channels can be set up to give improved data services.