1. Medium occupancy as coexistence metrics
July 2008
Medium occupancy as coexistence metrics
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2. Scope Enable the general discussion on the “medium occupancy metrics”
July 2008
Scope
Enable the general discussion on the “medium occupancy metrics”
Related to coexistence only?
Criteria on “good” coexistence
Discuss it in the context of “coexistence definition”
IEEE – 2003 Recommended Practice:
“3.1.2 Coexistence: The ability of one system to perform a task in a given shared environment where other systems have an ability to perform their tasks and may or may not be using the same set of rules.”
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3. Causes of high medium occupancy
July 2008
Causes of high medium occupancy
Service parameters
High offered traffic
High coverage target
Low modulation and coding rates
Interference and hidden nodes
High percentage of packet loss
High retransmission rate
Bad inter-operator coordination (antennae mounting, parameters, tilts, etc.)
Protocol un-efficiency
Conclusion
High medium occupancy is reflecting an attempt of the operator to “perform their tasks” while using the available technologies
The attempt may or may not affect the coexistence with other systems
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4. Example of good coexistence
July 2008
Example of good coexistence
Transmissions in this area do not interfere
Suitable antenna orientation in these areas to avoid interference
Full time medium occupancy
Space isolation
Suitable antenna orientation
Statistical distribution in space of transmitters and receivers
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5. Effects of limited medium occupancy
July 2008
Effects of limited medium occupancy
Throughput:
Highly reduced due to lack of time
Highly reduced due to hidden node effects
Retransmissions
Coverage
Reduced
Latency
Increased
Conclusion
Systems does not “have an ability to perform their tasks”
No coexistence
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6. Efficiency of limited medium occupancy
July 2008
Efficiency of limited medium occupancy
Bursty traffic
Low offered traffic load for one system and high offered load for another system
Different needs for medium occupancy as function of time
There is no need for “limited medium occupancy”
CBP is doing well without a priori limiting the medium occupancy
Conclusion
Systems do not “have an ability to perform their tasks”
Advantages of the statistical multiplexing are canceled
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7. July 2008
General Conclusion
Medium occupancy is an ambiguous metric for coexistence
May be high occupancy, but good coexistence
Limitation might be un-necessary in many scenarios
Dynamic sharing is affected by “limited occupancy”
Limited occupancy may negatively impact
systems may not “have an ability to perform their tasks”
High medium occupancy is reflecting an attempt of the systems to “perform their tasks” while using the available technologies, but not the coexistence itself
Proposal
Remove the “Medium occupancy” metrics from the 3.65GHz coexistence assurance
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