Dr. Mark Humphrys

School of Computing. Dublin City University.

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Uses of Wireless

Fixed wireless broadband

Wireless LAN


The mobile phone system

2.3 Wireless

Fiber optic may eventually dominate the cable world,
but it will never dominate all comms.

The future is fiber optic and wireless.

Uses of wireless:

  1. laptops, notebooks, palmtops, PDAs, mobile phones
    1. on aircraft, in cars, at sea
    2. in airports, cafes, at conferences
    3. on the beach, in mountains, fields, remote areas

  2. Work
    1. Mobile workers - taxis, fleets, trucks, ships, aircraft
    2. Military - bring your own network with you - don't rely on local one.

  3. Mobile-specific services
    1. GPS phones (and here)
    2. iPhone applications
    3. All iPhone applications - see Navigation
    4. Where is nearest shop to where I am now?
    5. Show me local street map.
    6. Whrrl, Google Latitude - Show me where all my friends are as dots on a map - find friends in streets nearby.
    7. Clothing with barcodes that can be read by any camera (don't need scanner). Point smartphone at them and barcode identifies them and can send you to their webpage on your smartphone.
    8. All this could lead to a return in urban areas to a "village" environment - where you can easily find people, and you know who and where everyone is.

  4. (Local area) alternative to cables
    1. Personal area network - connecting PC keyboard, peripherals (as alternative to cables)
    2. Wireless home network - feed broadband Internet access to multiple PCs and laptops, which may be moved from room to room

    3. wiring a building where installing cable is difficult (e.g. old building, remote building)
    4. Similarly, fixed location where installing line is too much overhead. e.g. Vending machine uses wireless to call home with its stock levels. Giving it its own phone line for 1 call a day is too expensive (install, monthly charge).
    5. Wireless home network - link small devices - fridge, TV, phone, burglar alarm, smoke alarm, security cam. e.g. Belkin WeMo.
    6. wearable computing

  5. (Wide area) alternative to cables
    1. alternative to laying long- (or even short-) distance cable (no right-of-way is needed, e.g. in crowded urban region)
    2. long-distance satellite links (as alternative to laying ocean cable)

    3. VSAT's (also here) - very small satellite:
      1. receivers (1-way broadcast satellite TV, GPS)
      2. and transmitters (satellite phones for remote areas, third world countries with poor telecom networks)

    4. Broadcasting of data in general - Satellite makes more sense than fiber.

Fixed wireless v. Mobile wireless

2.3.1 Frequencies

Summary of electromagnetic spectrum.
To the left: long wave, low f.
To the right: short wave, high f.

Useful f's for data

Can use these to send data, in order of increasing frequency:
  1. radio - lower f - lower bandwidth
  2. microwave
  3. infrared
  4. visible light (fiber optics) - higher f - higher bandwidth

Higher f than visible light are dangerous to humans. Not used.

High f absorbed or blocked by objects

  1. radio - low f, passes through walls etc.
  2. microwave - ok at low f - at high f is absorbed by water (rain)
  3. infrared - higher f, can't pass through walls
  4. visible light - even higher f - obviously can't pass through walls

So in practice:

  1. radio - lower bandwidth

  2. microwave - the most useful
    • mobile phones
    • wireless local loop (fixed wireless)
    • satellites - TV, telephone backbone, Internet backbone
    • on land, long-distance telephone links (most long-distance links before fiber optics),
    • at high f is absorbed by water (rain) - have to route around / correct errors

  3. infrared - can't pass through walls
    • remote controls, car keys
    • connecting peripherals, e.g. cordless mouse

  4. light - can't just send through air - have to send in fibers

Why is wireless different?

Lots of issues, such as:

2.5.3 Fixed wireless

Wireless local loop.
Way to break telephone company monopoly of local loops.

Fixed wireless - e.g. in the home.
User doesn't move. No problems like mobile phone handoff.
High f microwaves.

Bandwidth massive (36 Gbps) but shared among many (thousands of) users of one tower.
See "contention ratio".

Reduced bandwidth the further you get from the base station.

WiMax - 802.16 goes mobile

The mobile phone system

Wireless LAN (WiFi)

People mobile, coming to fixed LAN locations.
Connect to local LAN (e.g. in cafe, at conference, in library) rather than connect direct to phone network as in mobile phones.

Strong competitor of mobile phone network (for data comms at least),
but wireless LAN "hotspots" may not exist where you want.

Semi-mobile user, going from base to base.

Competitor also of Ethernet cable LAN - much easier to install.

Wireless home network - feed broadband Internet access to multiple PCs and laptops, which may be moved from room to room

Wireless to replace cables


Cordless mouse, keyboard, headphones, etc.

PDA file synch.

Wireless hands-free mobile phone headset.

ancientbrain.com      w2mind.org      humphrysfamilytree.com

On the Internet since 1987.

Wikipedia: Sometimes I link to Wikipedia. I have written something In defence of Wikipedia. It is often a useful starting point but you cannot trust it. Linking to it is like linking to a Google search. A starting point, not a destination. I automatically highlight in red all links to Wikipedia and Google search and other possibly-unreliable user-generated content.