ODMA

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ODMA

• Opportunity Driven Multiple Access

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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.

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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.

Repeater
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Urban Environment Model
250 m
250 m
BTS
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
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System Performance Free-space Model
(Attenuation kd-2)
-60.00
-65.00--60.00
-65.00
-80--70
-70.00--65.00
-90--80
-70
-75.00--70.00
-70.00
-100--90
-80
-80.00--75.00
-110--100
-90
-85.00--80.00
-120--110
-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
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System Performance Urban Model (Attenuation
kd-4 )
-30--20
-30.00
-40--30
-50--40
-35.00--30.00
-35.00
-60--50
-20
-40.00--35.00
-30
-70--60
-40
-45.00--40.00
-50
-40.00
-80--70
-60
-50.00--45.00
-90--80
-70
-55.00--50.00
-80
-100--90
-45.00
-90
-100
-110--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
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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.

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Number of Calls per Cell Manhattan Grid Model
30
With Repeaters
25
Without Repeaters
20
15
10
5
0
2
2
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Required Transmission Power per Link Manhattan
Grid Model
-10 dBm
With Repeaters
Without Repeaters
Linear Scale
-36 dBm
0
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Total Transmission Power per Cell Manhattan Grid
Model
-7 dBm
With Repeaters
Without Repeaters
Linear Scale
-21 dBm
0
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TDD Frame Structure for ODMA Operation
10 ms
4.096
Mchip/s
625
m
s
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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.

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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 RD 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
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