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Coexistence in Licensed Bands Issues & Methodologies

Coexistence in Licensed Bands Issues & Methodologies

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Coexistence in Licensed Bands Issues & Methodologies

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  1. Coexistence in Licensed BandsIssues & Methodologies IEEE 802.19 Meeting May 2004 Joanne Wilson Reza Arefi Joanne@arraycomm.com reza.arefi@ieee.org Joanne Wilson & Reza Arefi

  2. Status of Coexistence Studies in IEEE 802 • Unlicensed • 802.15.2 produced coexistence guidelines • 802.19 TAG was formed to address unlicensed band coexistence between wireless 802 projects • Licensed • 802.16.2 produced a Recommended Practice (and its revision) to address intra-802.16 licensed band coexistence • Very limited scope • No definition of coexistence is provided • 802.20 • Coexistence CG was formed in July 2003 • The WG voted to hold off on Coexistence work in November 2003 Joanne Wilson & Reza Arefi

  3. Licensed bands • 802 projects for licensed bands (802.16 and 802.20) deal with metropolitan/wide area networks with multi-cell deployments • Coexistence with geographical and/or spectral neighbors is key to successful deployments in licensed bands • Objective is to create guidelines for preventing from harmful interference by determining levels of permissible, or acceptable, interference • Interference environment varies with deployment scenarios Joanne Wilson & Reza Arefi

  4. Deployment Scenarios • Deployments could be under nation-wide licenses • Deployments are likely to have multiple operators with potentially different systems : • in the same service area • In adjacent service areas (domestic as well as international) • Deployments in or adjacent to bands already used for commercial services are also likely • Cellular, PCS, 3G, Radar, P-P links, broadcast • No shared environment • Co-channel in adjacent areas, or • Adjacent channel in same area, but • No co-channel in same area Joanne Wilson & Reza Arefi

  5. Specifics • From regulatory point-of-view, licensed co-channel operation in the same geographical area would not be allowed • Cognitive Radios? • Possibilities • Co-channel across service boundary: geographical neighbors • Adjacent channel within same service/geographic area: spectral neighbors • Neighbor could be non-802.xx or same 802.xx but of a different duplex • It could be assumed that geographical and spectral neighbors of the same duplex have much easier time coexisting with each other with reasonable coordination • frame synchronization, power at service boundary, etc. Joanne Wilson & Reza Arefi

  6. 802.xx TDD Lower neighbor Lower neighbor Upper neighbor Upper neighbor 802.xx FDD 802.xx FDD Middle neighbor(s) Spectral Neighbors, Same Area • 802.xx systems may need to coordinate with spectral neighbors • The number and the nature of spectral neighbors TDD and FDD systems may need to coordinate with are not necessarily the same Joanne Wilson & Reza Arefi

  7. System System 1 2 Blue: intended Red: interference Service boundary Geographical Neighbors, Same Frequency • Service areas for licensed spectrum typically don’t overlap, but exceptions do exist • Protection, in Service Rules, is typically through power limit at service boundary, which may or may not be sufficient • Interference scenarios (general) • Base-Base • Sub-Sub • Base-Sub • Sub-Base Joanne Wilson & Reza Arefi

  8. f f TDD-FDD Issues • Coexisting of FDD systems (co- or adj-channel) • Base-Sub • Sub-Base • For TDD-FDD or unsynchronized TDD-TDD case: • Examination of Base-Base and Sub-Sub scenarios are also required • Safe distance needs to be determined Joanne Wilson & Reza Arefi

  9. Service Rules • For each band, out-of-band emissions and service boundary levels are specified by regulatory authorities as Service Rules • Implementations of 802.xx in each band should adopt these values to comply with the rules unless shown to be inappropriate, where more stringent levels should be used • Example, service providers are voluntarily using tighter specifications than the rules require in the PCS band • Receiver performance, including filters, are typically not specified by the regulators • Assumptions on these are, however, required to perform coexistence analyses • Interference temperature? Joanne Wilson & Reza Arefi

  10. Methodology • Pick a few “primary candidate” bands • Perform simulations using typical equipment specifications • Requires feedback from the WG on parameters such as TX power, RX thresholds for various modulation schemes, ACS, ACLR, etc. • Needs network of cells, e.g. two tiers, with users distributed throughout the cell coverage areas Joanne Wilson & Reza Arefi

  11. Methodology • Given PHY parameters and appropriate path loss models, links to every user is being set up incorporating power control loops, burst profile (mod/coding class) as dictated by SINR conditions, etc. • A snapshot of impact of interference on a victim (Base or Sub) is then captured • Impact on outage • Impact on capacity (throughput) • The process is then repeated many times to reveal the statistics of interference Joanne Wilson & Reza Arefi

  12. Methodology • Sample CDF plot Outage threshold Interference threshold : Safe area (acceptable interference) Joanne Wilson & Reza Arefi

  13. Methodology • If following the Service Rules does not provide for adequate protection, then recommend new guidelines through: • Determine “safe” geographical and/or spectral distance between the two potentially interfering systems for acceptable operation under the Service Rules • Determine TX/RX parameters that enable “safe” operation in geographical and/or spectral adjacency Joanne Wilson & Reza Arefi