Last Mile Access

Last-Mile Internet Access #

Def.: The final leg between the telecommunications network (cable, Internet, etc) and the end user (home, university, cellphone, etc)

  • Tends to be the most bandwidth-constrained, as it costs lots of money to invest in infrastructure to everywhere

History of last-mile #

  • Early 90s: 56k dialup was the way to connect
    • Leveraged existing telephone network to connect homes to the internet
    • However: very slow, and restricted by modems themselves - 56kbps was theoretical maximum, in reality was ~30-40kbps
    • Also: Could not use phone and internet at the same time
  • Late 90s: Digital Subscriber Line (DSL)
    • Different frequency channel (so different hardware) - allows people to use phone and internet at the same time
    • Early on, up to 256k speeds
    • Much of the world still uses DSL
  • Early 00s: cable internet
    • Core idea: use cable television network for internet; typically copper cables or copper/fiber hybrid
    • 80% of Americans use cable to connect to “broadband” (defined by FCC as stable, 25mbps DL, 3mbps UL, but term has been diluted by cable companies)
      • Even still, 21M Americans don’t have broadband access; 1/2 of global population does not either
    • Caused cable TV companies to become ISPs
  • 2010s: Fiber-to-the-Premises
    • Available in densely populated areas in developed regions
    • Major US, European players, e.g. Google, Verizon, etc; smaller players are getting in as well
    • However, very costly: $27k per mile of fiber
  • Main areas of investment:
    • Wired (cables)
      • Copper, coax at last mile, but could be fiber in developed regions
      • Fiber in backhaul/backbone
    • Wireless
      • Satellite
      • Cell towers
      • New moonshots

Telecom topology #

  • National backbone network (core): submarine cables that terminate at points of presence (PoPs)
  • Middle-mile network (backhaul): satellite, fiber, or cellular connections terminating at base station tower or local PoP
  • Last-mile network (access): wireless/wired connection to home or cellular divice

“Dig-Once” policies #

  • When doing other infra. projects (e.g. construction, sewage), build in broadband connection you need instead of separately
    • Estimated to save $126B of $140B of nationwide fiber cost
    • However: only 16 states have implemented policies - CA included
    • Nationwide legislation stonewalled, due to lobbying from larger telco providers as the policies would give smaller regional providers low-cost access to building fiber

Mobile networks #

  • Exploded in popularity in the last 20 years as cheaper alternative to broadband access than fiber
  • 4G networks offer broadband speed, but expensive to build: ~$200k per cell tower
  • Generations (every generation, ~10x increase in bandwidth):
    • 1G: basic voice calling services
    • 2G: Voice calls, text messages, limited browsing
    • 3G: Broadband, video conferencing, GPS
      • 4G LTE: “Long-Term Evolution” transition phase to 4G, but not actually 4G
    • 4G: high-speed apps, mobile TV, wearable devices
    • 5G: HD streaming, IoT, autonomous vehicles

5G networks #

  • More than just increased bandwidth compared to 4G; 5G networks are expected to eventually support:
    • Enhanced mobile broadband: extreme data rates, extreme capacity
    • Mission-critical control: ultra-low density, ultra-high availability, extremely mobility
    • Massive IoT: devices with ultra-low energy, ultra-high density
  • Improvements in how data is multiplexed onto radio spectrum
  • New frequency bands: Higher frequency generally means faster data rates, but less coverage and range

Cloudification of access #

  • Cellular networks have been historically extremely opaque: proprietary hardware, slow to innovate
  • Industry is re-architecting access network using principles of SDN: run 5G network functions in the cloud rather than on purpose-built applications
    • Win-win: network operators get faster innovation and CAPEX savings; cloud providers get low-latency connectivity to end-users on their devices

Satellite networks #

  • Works through connection of satellites (often privately operated) that are flying in geostationary orbit (35km above)
  • Connections are SLOW
  • Costly to build, deploy, and operate, and thus costly to purchase
    • 25mbps from Comcast: $30/mo (in theory)
    • 25mbps from Viasat: $150/mo

Internet encroachment on TV spectrum #

  • In ~2007: researchers started to look into using TV (lower-band) channels for long-range communication for Internet connectivity
    • Lower band: can travel greater distances and move over more obstacles; cheaper to deploy and requires lower base stations
  • Idea: use whitespaces (gaps in TV-allocated frequencies)
    • Protests from TV companies, until FCC cleared the concerns in 2019