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TVWS Coexistence: Addressing the Spectrum Sharing Challenge

This tutorial discusses the coexistence of licensed and unlicensed devices in TV white spaces (TVWS), explores the need for coexistence, and presents approaches to address the spectrum sharing challenge.

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TVWS Coexistence: Addressing the Spectrum Sharing Challenge

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  1. 802.19 Tutorial – Use Case Draft 1 Authors: Date: 2010-07-08 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. Alex Reznik (InterDigital)

  2. Abstract • Draft of my tutorial slides for July tutorial • For discussion by the group Alex Reznik (InterDigital)

  3. Coexistence in TVWS: What is it? • TVWS presents a complex regulatory environment • Licensed devices: allowed to use the spectrum whenever, following appropriate rules • Unlicensed devices: permitted to use the spectrum when it is not occupied by licensed devices • Licensed and unlicensed devices do not coexist • Licensed devices make no special allowances for unlicensed devices • Unlicensed device must “protect” licensed operation by regulation • Protection of licensed devices is a medium access problem • Thou shall not access access spectrum when these guys are around Alex Reznik (InterDigital)

  4. Coexistence in TVWS: So what is it then? • Coexistence happens between peers • In TVWS, these are unlicensed devices and networks • Not mandated by regulations • Impetus must come from mutual benefit consideration: higher spectrum efficiency for all involved • Why do they need to coexist • Once available channels are known, the various networks and users need to decide – who goes where • This cannot be static – channel availability will change • Who specifies how this can be done • Some (not all) standards specify how different networks using same technology coexist • 802.11, 802.15 do this • Do they do it well?? • Some standards don’t even do that • cellular standards do not specify how different operators use the same spectrum • No MAC/PHY standard specifies how other MAC/PHY standards should behave • Nor should one MAC/PHY do it – it would rule over all the others • This void is filled by standards such as 802.19.1 in TVWS Alex Reznik (InterDigital)

  5. The Coexistence Problem: #1 “… you know you could help me out here. If you are on WiFi, if you could just get off…” “… we figured out why my demo crashed. Because there are 570 WiFi base stations operating in this room…” Steve Jobs see e.g. http://www.youtube.com/watch?v=yoqh27E6OuU • So many talkers … • … and no common language to discuss sharing Alex Reznik (InterDigital)

  6. The Coexistence Problem: #2 • So little spectrum … • So many ways to use it … 802.22 802.11 • How we addressed in ISM bands • “Smart hopping” by Bluetooth • More robust (lower) bit rate by WiFi • But such “autonomous” approaches may not work with 802.22 and WiFi • 802.22 can operate at up to 4W EIRP • WiFi does not frequency hop Bluetooth Bluetooth 802.11 802.11 802.11 Alex Reznik (InterDigital)

  7. The Coexistence Problem :#3 • Few people – many channels … • Many people – few channel … Source: Mishra and Sahai, IEEE Comm. Letters, 2009 Source: Gerami, Mandayam, Greenstein. Report by Winlab, Rutgers U., 2010 Alex Reznik (InterDigital)

  8. Operation in TV Bands: Why Deal With the Headache? • TV Band Spectrum presents unique opportunities and possibilities • Potentially a lot of spectrum • But availability not guaranteed • Excellent propagation characteristics • Cover large distances • Penetrate walls, obstacles • So what could this be used for • Find additional bandwidth for data networks (in those areas where TV channels are many) • Offload to free up valuable (licensed) spectrum • Quick and cheap network deployment: cover a large area with few access points and little planning • Cheap spectrum for applications requiring only intermittent communication Alex Reznik (InterDigital)

  9. Example Use Case 1:Rural/Suburban Home/Small Office Source: Sum et. al., IEEE doc. Scc41-ws-radio-10/5r0, IEEE SCC41 Ad Hoc on WS Radio Usage Models, 04/2010 Alex Reznik (InterDigital)

  10. Example Use Case 1: Rural/Suburban Home/Small Office • Potential Uses • Device-to-Device (Machine-to-Machine) • WLAN Access • Backhaul • Cellular offload • Characteristics • Single operator controls much of the network and controls the space • Limited interference from like networks • Requires high data rates/no critical usage applications • Is this a good fit for white spaces • Yes, if the channels are available • Yes, if the operator (home owner) can automate the channel selection and coexistence of the various technologies he owns Alex Reznik (InterDigital)

  11. Example Use Case 2: Apartment • Similar usage to the home use case, but very different environment • Multiple operators • Each resident operates own network • No incentive to cooperate/coordinate • WWAN network may be overlayed into this space • Little spatial separation between the operators • Lots of networks crammed into a small spaces • Opens the possibility of the iPhone4 demo problem • Is this a good fit for white spaces • Maybe – but the inter-network coexistence problem will definitely need to be solved. Source: Paine et. al., IEEE doc. 802.19-09/26r4, Whitespace Coexistence Use Cases, 07/2009 Alex Reznik (InterDigital)

  12. Example Use Case 3: Utility Grid Source: Sum et. al., IEEE doc. Scc41-ws-radio-10/5r0, IEEE SCC41 Ad Hoc on WS Radio Usage Models, 04/2010 Alex Reznik (InterDigital)

  13. Example Use Case 3: Utility Grid • Potential uses • Collection of metered data • Reporting of aggregated data over the backhaul • SCADA support • Characteristics • Relative low-rate, can deal with intermittent outages • Single network operator, but spanning a large distance • High likelihood of interference with different network – this interference varies in nature and spectral location throughout the network • Is this a good fit for white spaces? • Absolutely • Covers large areas • Meters may need to penetrate obstacles • Requires only intermittent connectivity Alex Reznik (InterDigital)

  14. Example Use Case 4: Public Safety Source: Sum et. al., IEEE doc. Scc41-ws-radio-10/5r0, IEEE SCC41 Ad Hoc on WS Radio Usage Models, 04/2010 Alex Reznik (InterDigital)

  15. Example Use Case 4: Public Safety • Potential Usage • Rapid deployment of emergency personnel networks • Inter-personnel communication • Network backhaul • Communication to the main office • Characteristics • High-rate data rate services • Multi-media and conversational services • Creating an “instant network” where there was none • Is this a good match for white spaces • Yes, IF spectrum can be found, need to have backup plans. • Yes: need to create a network with few APs and no ability to plan • Yes: need penetration through obstacles • Yes: need the reach the main office Alex Reznik (InterDigital)

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