Facilitating Power Line Communication PHYs

1. Facilitating Power Line Communication PHYs Authors: Date: 2008-05-13 Clint Chaplin, Samsung Electronics

2. Abstract There exists several consumer and SOHO use cases where wireless communication cannot reach with sufficient bandwidth and it is impossible to pull new wiring. One possible solution is powerline communication (PLC). Powerline communication usefulness could be facilitated by combining an 802.11 MAC with a powerline PHY Clint Chaplin, Samsung Electronics

3. Problematic Use Case • There is a need for reliable 20Mb/s communication across a home or small office. • Home may be 100 feet end to end • Home construction may block radio • Households are buying their second HD TV; usually in master bedroom • Some video codecs data rate is 20Mb/s; don’t want to have to transcode video • Home may not allow new wiring to be pulled; historic buildings that cannot be modified, walls cannot be drilled, etc. • May need 60Mb/s capacity to give a reliable 20Mb/s Clint Chaplin, Samsung Electronics

4. Existing Technologies Fall Short • 802.11n at 100 feet does not approach 20Mb/s • Current equipment tested capacity falls short • 60GHz is essentially line of sight and effective only within a single room (UWB has same problem) • Dramatic dropoff (to the fourth power) vs. distance • Current regulatory limits on transmitted power coupled with Shannon’s limit show little promise for wireless solutions • Wireless bridges essentially split total available bandwidth between uplink and downlink Clint Chaplin, Samsung Electronics

5. Powerline Communication (PLC) • Powerline communication within home or small office is one possible solution • Does not need any new wires to be pulled • Throughput vs. distance is better than regulatory constrained wireless Clint Chaplin, Samsung Electronics

6. Similarity of 802.11 and PLC • The In-Home medium (power lines) is similar to the 802.11 medium • Shared medium • High loss ratios • Open, unlicensed “spectrum” (open access to all kinds of devices) • Uncontrolled medium: no clean definitions of cable types and terminations • Multipath • Interference from external devices • Power drills, vacuum cleaners on PLC versus microwave ovens on 802.11 • Interference on external devices • PLC on short wave radio versus 802.11 on radar, 802.15 and 802.16 • Indeterminate edges on the medium: both extend through various types of physical boundaries • Wireless extends through walls • Wired extends outside the “In-Home” – into neighboring apartments • But also is dissimilar from the 802.11 medium • Wires • Only one channel – no channel hopping • 2-30 MHz band at usable power levels; up to 100Mz at lower power levels • Different noise sources; different noise patterns • Different attenuations: twisted cap connection to the second bedroom; fuse boxes • Blocking filters are possible – but not yet available • No legacy standards • Access technology interface – requires In-Home to support some level of coexistence / interoperability Clint Chaplin, Samsung Electronics

7. Current State of PLC • The new idea (last few years) • 200 Mbps PHY raw rate; 50+ Mbps above MAC (UDP) • CSMA/CA – EDCF-like • QoS is HCF-like: both parameterized and prioritized • Beacons, CFP, CP, polling • Network manager (AP-like) access control, security and QoS • Three variants of the new idea • All are proprietary, but not that far apart from each other • PHYs use versions of OFDM • MACs can encapsulate Ethernet frames in MSDUs Clint Chaplin, Samsung Electronics

8. Natural Synergy: 802.11 MAC and PLC PHY • The PLC DS for 802.11 will fully support 802.11 • 802.11i / 802.1X security (including authentication server) authorizes all PLC STAs, as well as 802.11 STAs • Unauthenticated equipment on the DS is a security hole in the overall system (ESS) • Using different authentication systems for 802.11 and PLC opens security holes • Bandwidth reservations over PLC • Continuous allocations from one WLAN across the DS to another WLAN • Same priorities over PLC: “Mapping” is one-to-one • Have a dead spot? Plug another AP into the wall. • Same security and QoS will be available from the gateway throughout the home • Or plug the mobile device (laptop, PDA, video player) itself into the wall. • 802.11r mobility domain can include the PLC network manager (AP) • Fast transition over unplugging from / plugging into the wall power • Seamless VoIP, video streaming sessions for laptops, PDAs, cordless phones • Applications see PLC as another available WLAN • If more bandwidth or a better connection there, application can trigger handover • Sudden congestion in one, application can skip to the other • Application doesn’t have to care whether each LAN is wired or wireless Clint Chaplin, Samsung Electronics

9. PLC MAC/PHY Services • 802.11-2007 PHY / MAC services, management entities • There’s not much there that is wireless-specific • Exercise left to the student: reread 802.11-2007 while thinking “really lousy wire” • PHY • PLCP, MPDUs, CCA, PLME, PMD-SAP; PMD, of course, is specific (to OFDM) • PLC can support a superset of the PHY-SAP, PMD-SAP • OFDM parameters, frames, symbols, preambles • Even RSSI has value on an “open spectrum” wire • MAC • HCF: both parameterized and prioritized QoS • Beacons, CFP, CP, polling, EDCA, RTS/CTS, NAVs, TSPECs • MSDUs, MPDUs, IFS (SIFS to AIFS), backoffs, TXOPs, block ACKs • MLME • Just imagine a really limited medium that has only one channel • And no need to detect radar • PLC can support a superset of the MAC-SAP and MLME • RLM • 802.11-2006 really is not about wireless • 801.11-2006 is an RLM  LAN recipe book Clint Chaplin, Samsung Electronics

10. Proposal • Add to the 802.11 Mac what few new interfaces and services are necessary to facilitate PLC PHYs • Essentially create a “snap-in” interface for a PLC PHY • Not necessary to actually define a non-wireless PHY in 802.11 Clint Chaplin, Samsung Electronics

11. Implications • PLC and 802.11 could be in the same ESS and same roaming domain • Only need a single authentication server for both PHYs. • Roaming between PHYs becomes trivial • Unplug a laptop, and trivially switch to wireless 802.11 • Layer 3 roaming no worse than 802.11 wireless roaming • AP can service both PLC and 802.11 wireless networks • With bridging function, can plug in a new AP anywhere there is power. • Single cable to AP; instead of power over ethernet, “ethernet” over power Clint Chaplin, Samsung Electronics

12. References Clint Chaplin, Samsung Electronics