1. Opportunity Driven Multiple Access
ODMA
Opportunity Driven Multiple Access
Raul Bruzzone

2. Opportunity Driven Multiple Access (ODMA) Introduction
ODMA is a Multiple Access technique that makes part of the UMTS Terrestrial Radio Access concept.
It is based on the use of Intelligent Radio Repeaters (also called “relays”).
Repeaters communicate with the Mobile Units, and between them, using the TDD mode.
Repeaters communicate with the Base Station using the FDD mode.
ODMA provides increasing radio capacity to cells located in Urban environments.
November 18
Raul Bruzzone

3. PATH DIVERSITY
In a Urban Environment, several radio paths co-exist between the UE and BS.
Significant variations in path attenuation may be expected.
If a Repeater is introduced in the radio path (Z), the power budget may be reduced in excess of 30 dB.
As the transmission power is reduced, interference to adjacent cell also diminishes.
This interference reduction may be traded as increased Cell Traffic Capacity. X X X Z Y
Repeater
November 18
ODMA1

4. Urban Environment ModelS S S S S M M S M S S S S M M
250 m S S
BTS S M S
100 Traffic Channels
available for each Cell S S S M S S M S S S S S M
M: Mobile - an ODMA mobile communicator (e.g. phone)
S: Seed - a Mobile which is fixed in position and continually powered
BTS: Base Station - a gateway to a fixed communications link
Node: - any of above
November 18
ODMA2

5. System Performance Free-space Model (Attenuation = k*d-2)
-60.00
-65.00
-70
-70.00
-80
-90
-75.00
-100
-110
-80.00
-120
-85.00
Total Power at Repeaters
(Relaying System)
Transmitted Power at Mobiles
(Non-relaying System)
Repeaters near the Base Station operate at higher power than those located in the periphery of the cell
Mobiles far from the Base Station operate at higher power than those located in the centre of the cell
November 18
ODMA2

6. System Performance Urban Model (Attenuation = k*d-4 )
-30.00
-35.00
-20
-30
-40
-40.00
-50
-60
-70
-80
-45.00
-90
-100
-110
-50.00
-55.00
Total Power at Repeaters
(Relaying System)
Transmitted Power at Mobiles
(Non-relaying System)
Repeaters near the Base Station operate at higher power than those located in the periphery of the cell
Mobiles far from the Base Station operate at higher power than those located in the centre of the cell
November 18
ODMA2

7. Conclusion:
A system based on Repeaters produce less co-channel interference on neighbouring cells, than other system that is only based on UE directly radiating to the Base Station.
November 18
ODMA2

8. Number of Calls per Cell Manhattan Grid Model30
With Repeaters 25
Without Repeaters 20 15 10 5 2 2
November 18
ODMA2

9. Required Transmission Power per Link Manhattan Grid Model
-10 dBm
With Repeaters
Without Repeaters
Linear Scale
-36 dBm
November 18
ODMA2

10. Total Transmission Power per Cell Manhattan Grid Model
-7 dBm
With Repeaters
Without Repeaters
Linear Scale
-21 dBm
November 18
ODMA2

11. TDD Frame Structure for ODMA Operation
10 ms
4.096
Mchip/s
625 m s
ORACH
Slot
ODCH
Relay Link
ORACH: ODMA Random Access Channel
ODCH: ODMA Dedicated Channel
November 18
ODMA3

12. Opportunity Driven Multiple Access (ODMA) Summary
In Urban environments, the infrastructure required to support given levels of coverage and capacity could be very significantly cheaper with ODMA than with a more traditional approach.
The mean transmission power can be reduced by up to 30 dB.
More efficient frequency re-use.
Variation of the locations of peak demand can be supported more efficiently, without having to supply capacity which is unused for most of the day. Similarly, high bandwidth on demand can be supplied efficiently.
Mixed bathing — i.e. multiple operators in the same cell — can be supported without the need for dividing spectrum between operators.
ODMA allows greater resilience to Base Station failure.
November 18
ODMA2

13. ODMA References ODMA1 ODMA (E20/97) K. Mayes, J. Larsen (Vodaphone)
ETSI UMTS Workshop. Sophia Antipolis. December 1996.
ODMA2 Characteristics of Opportunity Driven Multiple Access (E21/97)
Vodafone Ltd, Salbu R&D Ltd.
TDOC SMG2 UMTS 30/97. March 1997
ODMA3 Physical channels and mapping of transport channels onto physical channels (TDD)
S1.21 V2.00 UMTS Specification Document
3GPP. April 1999

14. coming next ...
Introduction to cdma2000
November 18
Raul Bruzzone