Fair Spectrum Sharing

1. Fair Spectrum Sharing Authors: Date:2015-1-12 Notice:This document has been prepared to assist IEEE 802.19. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Alireza Babaei, CableLabs

2. Abstract • This document intends to start the discussion on defining a criterion for fairness across users or systems that horizontally* coexist in a shared spectrum (e.g., in unlicensed bands). * Horizontal access:Systems coexisting in the shared spectrum have equal regulatory status, for example systems that operate in unlicensed spectrum ** Vertical access:Systems that share the spectrum could have priority over one another (e.g., coexistence of primary and secondary systems). Alireza Babaei, CableLabs

3. Background • An interest group on “Fair Spectrum Sharing” was created in 802.19 working group during the November 2014 plenary meeting. • The purpose of IG is “to develop an IEEE 802.19 approved document defining and specifying how to measure fair spectrum sharing between networks, designed to different standards, operating in unlicensed spectrum” Alireza Babaei, CableLabs

4. Scope of Fair Spectrum Sharing Document • The “fair spectrum sharing” document should define a criterion that takes as input a given instance of spectrum usage pattern of the systems or users in the shared spectrum and delivers as output a measure of fairness for this instance of spectrum sharing. f How fair? X% fair Fairness Criterion spectrum usage pattern in frequency and time B t Alireza Babaei, CableLabs

5. Fairness across systems or users? • Two approaches can be followed when defining the fairness criterion: • First: Usersof the shared spectrum, irrespective of what access technology (AT) they use, and interfering with each other must have fair access to the wireless resources. • Second: Systemsoperating in the shared spectrum and interfering with each other must have fair access to the wireless resources. Alireza Babaei, CableLabs

6. Impact of Interference Range • Consider n systems (or users) sharing the spectrum. • Due to differences in power level among the systems (or users), in general, each system (or user) is in interference range of m (m ≤ n-1) systems (or users). • Fairness criterion must take into account the differences in interference range of systems (or users). Node: System or User Full mesh- each node is in interfere all other nodes (m = n-1) Partial mesh- each node is Interfered by a subset of other nodes (m < n-1) Alireza Babaei, CableLabs

7. Differences in Resource demand • Fairness criterion must take into account the differences in resource demands of different systems (or users) sharing the spectrum. John Doe, Some Company

8. Impact of Protocols on Fairness • Spectrum usage is highly impacted by the access protocol used by each system or user (e.g., TDMA, CSMA/CA, OFDMA, etc.). • The fairness criterion should be independent of the protocol details (PHY layer or access protocol) in each system. • Protocols or spectrum sharing rules to enable fairness across systems or users of the shared spectrum are outside the scope of this document. Alireza Babaei, CableLabs

9. Time-bandwidth product • The scope of fairness criterion should include the product of • Bandwidth occupancy (total including the guard bands) divided by the total spectrum in the band/channel • Total occupancy duty cycle Example: System “A” occupies 40% of the band 20% of the time- i.e., a 0.08 occupancy System “B” occupies 1% of the band 100% of the time- i.e., a 0.01 occupancy System “C” occupies 100% of the band 100% of the time- i.e., a 1.00 occupancy John Doe, Some Company

10. Fairness requirements (full-mesh interference) • Consider n systems (or users), sharing the spectrum. • Consider a full-mesh interference scenario (i.e., when each system (or user) is in interference range of all other systems (or user)). For fairness across systems (or users): • When observing the n systems (or n users, irrespective of AT they are using) sharing the spectrum for a long enough period of time, each system (or user), provided that its resource demand is larger than or equal to the equal share of resources (total wireless resources divided by n), must have used equal amount of wireless resources. • If any of the systems’(or users’) demand is less than an equal share of resources, it should receive as much wireless resource as it demands. • If a system (or user) does not need a resource at a given moment, it must relinquish the resource so other systems that may need it may share it. Alireza Babaei, CableLabs

11. Conclusions • The fairness criterion should be defined for fairness across users of the spectrum (irrespective of their AT) and/or across systems operating in the spectrum. • The fairness criterion must take into account the interference range of each system (or user). • Fairness criterion for partial-mesh interference is open for further discussions • The fairness criterion should look at the spectrum usage pattern of systems or users (ratio of occupied spectrum over total available spectrum times the duty cycle of spectrum occupancy) for a long enough period of time. • Protocolsor spectrum sharing rules to enable fairness across systems or users of the shared spectrum are outside the scope of this document. Alireza Babaei, CableLabs

12. Straw Poll Fairness principles discussed in this presentation should be the basis for developing a fairness criteria Agree: Disagree: Abstain: Alireza Babaei, CableLabs