GPRS/3G versus WiFi: Feedback
Written by: Jonathan Briggs
February 12, 2006 [11485 views]
A big thanks to over 100 of you who completed the exercise on time. It appears that many of you spent more than my estimate of 2 hours completing it but those who have seem to feel it was worthwhile.
You will not be asked to remember exact numbers (distances, prices, speeds etc) for different technologies but as a professional working in this area you should have a feel for their different capabilities. That means being able to select from the technologies for different business applications.
Speeds of mobile technologies (from a customer point of view)
GSM Modem 9.6 – 14kb/s but typically 9.6kb/s too slow for web browsing
GPRS 56 – 114kb/s but typically about 33kb/s similar to dial-up modem speeds for PCs, suitable for web browsing
3G 384kb/s but typically about 144kb/s less than typical ADSL broadband speeds for PCs but adequate for streaming music and video (under ideal conditions)
802.11b (WiFi) 11 Mb/s (11000kb/s) – typically 4 Mb/s connection between base station and handset/laptop
802.11g (WiFi) 56 Mb/s (56000kb/s) – typically closer to the same speeds as 802.11b
802.16 (WiMax) 70 Mb/s (70000kb/s) – over much wider distances than WiFi
Notice the difference between theoretical speeds and typical speeds. Theoretical speeds operate only under laboratory conditions. In real life the speeds will always be much slower because of interference, distance and obstacles.
Also notice that WiFi speeds do not indicate the connection speed to the Internet which could be much slower. If I have a WiFi wireless connection in my home connected to a 512k ADSL connection, my download speeds can never be faster than directly connecting to the ADSL with a cable.
Distances from base-stations/cell towers
Speed is only one part of the equation. To provide Cell or WiFi networks companies must provide base stations. Cellular mobile base stations may cover an area of 1-2 km radius while WiFi base stations cover less than 100 meters. WiMax may extend this up to 10-30 km. a useful site for information on mobile masts
Use your common sense when thinking about recommending one of these two technologies.
Why is the speed of data transmission important?
This should be obvious. Different applications need different speeds. Some applications (such as VoIP) are time critical and won’t work at all if the data rates are too slow, others such as SMS and email don’t rely on sustained speeds. Use your own experience of the Internet to think about speed: live video, streaming audio, animation and realtime interaction need fast speeds. Notice that downloaded audio and portable video do not need high speeds because they are held in the device rather than ‘streamed’.
How are customer charged?
You need to think about different groups of customers. A customer who buys a WiFi base station for home or office is not charged for data transmission over WiFi. A customer who accesses the Internet over a WiFi connection at the airport is normally charged for time. Typical costs are £5-6 for 1 hour of connectivity. Watching a movie streamed over a WiFi connection would probably cost about £12. Some companies provide “all you can use” monthly costs for WiFi access and allow access on multiple nodes/networks.
Mobile data costs are typically charged by data transferred rather than by time. Operators are charging 60p-£2 for each MByte of data. A 400MByte Movie download would cost £100s. Mobile TV offers streamed video content for less than the data costs. Orange offers 20 hours of video for £10 per month.
Notice that prices are decided by the operators largely based on what they believe customers will pay for. If customers have devices that allow them to watch movies then the cost of data (for this application) has to fall.
How could WiFi be used to make telephone calls?
Many people already use Skype or other VoIP services to make calls over the Internet. The cost of this data application is included in whatever broadband subscription you are paying. Using a public WiFi hotspot would therefore incur the normal access costs (around £5 per hour). This is expensive for local Skype-Skype calls and cheaper than mobile for international. Remember that Skype and other services charge for calls to landline/mobile phones.
Can you see that this presents huge problems for the mobile operators who make their money from their call charges? They need to decide whether they are in the call business or the data business and if they are in the data business whether they charge for data or time.
As you noticed there are moves from the handset manufacturers and the networks to start to offer WiFi compatible phones (and datacards). Customers will be confused however if there are two different ways of making calls. BT have launched a mobile phone that switches onto your home WiFi network when you are at home. You are charged normal call rates from home and mobile outside. This is just one possible pricing model – expect many more.
What are the main problems with WiFi?
Security, interference, roaming and charging models are probably the main issues. The technology works on a public (shared) area of the radio spectrum rather than the dedicated frequencies of mobile. WiFi is also highly insecure although later versions allow encryption and passwords. There is a community WiFi movement that encourages open shared networks. Instantaneous roaming (handing connections from one base-station to another) is not standard for WiFi. It is therefore unsuitable for moving applications.
How can WiFi be used in a train but not in a car?
The Wifi service inside a train is a stationary application. The base stations are fixed inside the train and satellite and mobile are used to communicate between the train and the Internet. How WiFi is provided on trains? Providing a similar service in a car would be unfeasibly expensive.
Selecting technologies for different applications
- A farmer accessing the weather forecast in the middle of a field
This is almost certainly GPRS because 3G coverage in rural areas is still patchy (expensive for the operators to provide). It will not be WiFi and you should be able to explain why.
- Wireless access in an airport lounge
This will be WiFi if provided by the airport. Business users may use their own 3G connections.
- Mobile access in a moving taxi
This is very unlikely to be WiFi (at least for now, might be WiMax later). It is likely to be 3G because GPRS speeds are really too slow for useful Internet access. The taxi is unlikely to be involved in providing the service.
- Video streaming to a handheld device in a museum
Think about who is supplying the service. If the museum is handing out the devices then WiFi makes the most sense and has the lowest cost. If they are relying on visitors having their own handsets then 3G makes more sense. GPRS is too slow.
You need to become adept at looking at a business problem and selecting a technology. Look at the opportunities and the barriers.
What do you think?
