Wireless

2.3 Wireless

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. GPS phones
   2. List of iPhone appications
   3. Where is nearest shop to where I am now?
   4. Show me local street map.
   5. Show me where all my friends are as dots on a map - find friends in streets nearby.
   6. 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.
   7. 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 - 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.

2.3.1 Frequencies

• Electromagnetic radiation

• Electromagnetic spectrum

Useful f's for data

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?

• Mobile phone pickup when switched on
• Mobile phone handoff

• Increased delay times (e.g. satellite round trips)
• Satellite handoff
• Satellite 2 Satellite routing of packets

• Increased errors (interference, weather)

2.5.3 Fixed wireless

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".

• wireless
  • fixed wireless broadband

• IEEE 802.16 Working Group

• Huge amount of errors:
  • Rain, snow and leaves absorb these high f microwaves.
  • Hence we do error correction, not just error detection.
  • Almost all networks just do detect and re-transmit. Here the re-transmit would have errors too. So have to try to actually correct.
  • Use Hamming codes for correction.

• Fixed-wireless broadband in Ireland:
  • Irish wireless broadband permits awarded
  • e.g. Irish Broadband wireless broadband ISP. "Irish Broadband is rolling out a .. wireless broadband network across the Dublin area. "High sites" form the building blocks of the network. Each high site comprises a tall building or mast equipped with a broadcast transmitter. Customers connect to the network using a small antenna on their roof. This antenna must be within line of sight of an Irish Broadband site." Unlike mobile phone signals, the signals cannot penetrate walls.
  • See Irish broadband speeds.

2.6 The mobile phone system

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

• Mobile phone standards
  • GSM
  • CDMA (and here)
  • 2.5G
  • GPRS (and here)
  • EDGE (Enhanced GPRS)
  • I-Mode (and here)
  • 3G (and here and here)
  • 4G

• Data transmission on the mobile phone network.
• Lots of competing standards. Check back in 5 years.

• SIM cards

Normal mobile phone

Public domain image from here.

• GPRS (and here) - "2.5G" - dialup speeds, e.g. O2 offers up to 53 k bps

• WAP (and here)
• WML

• Limitations of WAP

• Google translates HTML to WML on the fly, so WAP users can view the Web, sort of.

• My links for my mobile phone (simple GPRS phone) shows how to view HTML pages, and how to make a phone number clickable.

Smartphone / PDA / Pocket PC

XDA Exec (and more images).

• 3G (and here and here)

• 3G speeds in Ireland
  • three.ie promises up to 3.6 M bps
  • Has anyone seen this in practice? On a laptop? On a mobile? On a PDA?
  • speed tests
  • mobile speed tests

• PDAs
  • Handheld PC
  • Tablet PC
  • Pocket PC
  • Smartphone

• Operating System
  • Windows CE (also here)
  • Windows Mobile

• Web browser
  • Microbrowsers
  • Pocket IE - Browse the web on PDA running Windows Mobile.
  • Opera Mobile - Browse the web on PDA running Windows Mobile.
  • Opera Mini - Browse the web on a simpler Java-enabled phone.

What I want

Wireless LAN

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

• CA Wi-Fi
• DCU Wi-Fi

• Wi-Fi
  • introductory FAQ

• IEEE 802.11 Working Group

• Wi-Fi
  • Security - WPA - need password to access the wireless network that you detect.
  • Can also set up restriction by MAC address.
  • There are 2⁴⁸ possible MAC addresses.

• How to find your MAC address
  • On Win NT/2000/XP:

    $ ipconfig /all
    

  • On Win 95/98:

    $ winipcfg 
    

• Hotspots (and here)
  • Ireland
  • Dublin Airport
  • Eircom hotspots (try here)

Wireless to replace cables

Cordless mouse, keyboard, headphones, etc.

PDA file synch.

Wireless hands-free mobile phone headset.

• Bluetooth short range wireless connectivity standard.

• IEEE 802.15 Working Group