Wireless

Fixed wireless broadband

The mobile phone system

Wireless LAN

Bluetooth

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 (since you have destroyed it!)

  3. Mobile-specific services
    1. Where is nearest shop to where I am now?
    2. Show me local street map

  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 - all device clocks can synch
    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

  3. infrared - can't pass through walls

  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.

2.6 The mobile phone system

Mobile user.
Handoff problems.

Extremely-mobile roving user (compare with semi-mobile user of wireless LAN).

Normal mobile phone

Can browse the Web, sort of.



Public domain image from here.

Web access on a WAP phone will look something like this.
Quite difficult to use, but ok if you want to look up something quick.
Public domain image from here.

Smartphone / PDA / Pocket PC

Medium-speed Internet through 3G when roaming.
Switch to high-speed Internet at Wi-Fi hotspots.



XDA Exec (and more images).

Web access on a Dell Axim X30.
See terms of use of image.

Web access on a Sharp Zaurus.
See terms of use of image.

What I want
What I want in a Handheld computer What I have now
hand-held or pocket-size device
Quality color graphics
Usable keyboard 		XDA Exec = HTC Universal
Windows Mobile
VGA screen (640 x 480)
Wi-Fi where available
mobile phone (3G) where no Wi-Fi
mobile phone (GPRS) where no 3G 		yes
Fixed rate (pay per month, not per minute or per kilobyte, and reasonable price) O2 3G prices - 40 euro/month for 2 G limit
always-on high-speed broadband Not really.

Wi-Fi - good when at a hotspot (e.g. 1 M bps seen)

static 3G (staying in one place) - slow - O2 say it is up to 128 k bps
typical bandwidth test says 60 k bps (same as fastest dialup)
GPRS up to 53 k bps

moving 3G (using it when commuting) - slow and erratic - keep losing connection - have to reconnect and even reboot every 4 miles or so

I am interested in an alternative to O2's slow and erratic service. If anyone else is providing unlimited 3G for under 50 euro per month, let me know.

Full-function web browser Pocket IE
telnet (ssh) PockeTTY
ftp (ftp browser) GetIt FTP
can I get a ftp browser?
(put remote ftp site on filesystem path, like WebDrive)
Full-function editor, normal desktop applications, etc. See software (and here)
Large (gigabyte) hard disk Standard SD cards, can buy 32 G card
normal file system yes
FAT32 with Long File Names
can copy website, browse it on disk, relative links work
Battery that lasts 1 week only a few hours, enough for commuting
Works in Ireland and abroad transparently no
- O2 unlimited package doesn't work abroad - have to switch to (very) expensive pay per megabyte
Sturdy, shockproof, waterproof not really

Wireless LAN

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

Short-range.

Cordless mouse, keyboard, headphones, etc.

PDA file synch.

Wireless hands-free mobile phone headset.