Wireless Networking in Nigeria

By – Sunday A Folayan

General Data Engineering Services Ltd, Ibadan

General Data Eng. Services

Started SKANNET in October 1996 with:• One laptop

• Two phone lines

• 3 dial-up clients by Nov 1. 1996

• Capital of N200,000. ($8,000)($1=N25 then)

SKANNET

…May 2001:• 2000 Turnover > N50m ($420,000)

• Fifty (50) dial-up phone lines

• 5,241 dial-up clients in Apr. 2001

• Over N30m ($250,000) Fixed assets($1=N125 Now)

Why use wireless?Inability to obtain more lines from the PTT

Available phone lines barely do 28.8kbps

Clients’ Demand for bandwidth greater than what the dial-up lines can support

Lack of alternative technology such as DSL or ISDN

Design Choices

Physical Layer: Infra-Red (IR) VS Radio Frequency (RF)

Technology: Frequency Hopping VS Direct Sequence

Frequency: 902 – 928Mhz, 2.4-2.483Ghz, 5.15 –

5.875GHz Access Method: TDMA VS CSMA Topology: Peer to Peer VS Base Station Access

The cost of getting equipment manufactured to specification is beyond the means of most African operators. We thus have to choose among products in the market.

SKANNET chose Cisco Aironet Products

Operates in the 2.4GHz ISM bandUses the Direct Sequence methodUp to 11Mbps data rateUp to 25Km (?) RadiusWired Equivalence Privacy

Equipment Sources

Equipment sources are mixed

Radio: Provantage - www.provantage.com

Antenna: Mikrotik - www.mikrotik.lv

Wireless Bridge

Workgroup Bridge

PCI Card

ISA Card

PCMCIA Card

Product Options

15dB Omni Directional base station antenna

and

24dB Directional Customer service

antenna

Antennas

Omni-directional Antenna is Elevated on a 120ft Mast

Indoor Equipment

Fits neatly into a 42U cabinet. Help Desk is in the foreground.

Service Options

Equipment 1. Outright Purchase2. Hire Purchase agreement with end-time

ownership3. Lease agreement. No end time ownership

Bandwidth 1. Pay-Per-Use bandwidth limited

Access2. 24x7 Bandwidth limited AccessBandwidth is sold Differentially (Internet/Intranet

)64K/8K is N30,000 ($240) per month.

Subscription

25

811

15

19

25

33

0

5

10

15

20

25

30

35

Oct-00 Nov-00 Dec-00 Jan-01 Feb-01 Mar-01 Apr-01 May-01

Bandwidth Management

Solution: Hardware/Software combo from Emerging Technologies Inc. www.etinc.com

Major Advantage: Management of bandwidth by MAC addresses, apart from IP Number. Has 5 of 100 Base T ports that can be individually limited.

Differential Bandwidth: Setting Internet Access bandwidth much lower than Intranet Access

Metering and Billing

1. The bandwidth manager has MRTG-like graphing utility, for examining the utilization pattern of each subscriber, either daily, week or monthly.

2. Using a simple PERL script running on the bandwidth manager, bandwidth utilization statistics are extracted for each subscriber

3. Summary of utilization is written to a mySQL database, which is read by the billing software

4. Another PERL script on the Bandwidth manager limits Expired accounts to 1kbps.

Excessive RF Cable Length leads to signal attenuation

Problems encountered

Solution: Keep RF cable to less than 15 meters. If length will be more than 15 meters, then mount Radio in a weather-proof case, close to the antenna and use a short RF cable.

Ferry the signal from the Radio, using Ethernet cable to the hub or router. Ethernet cable can be as long as 300ft.

Bulky power system and cabling to Weatherproof case

Problems encountered

Solution: Use pairs 4/5 and 7/8 of the Ethernet cable to carry 18V DC required to power the Radio.

Power drop is not a problem, since Cisco Aironet radios operate from 12V to 18V.

Costant power to run the Repeater stations

Problems encountered

Solution: Use a mixture of Solar and Wind power where there is erratic public utility supply

Further reading …Wireless Local Area Network (LAN) tutorial. http://www.wirelesslan.comWireless LAN design alternatives by David F. Bantz and Frederic J. Bauchot.

http://www.cs.berkeley.edu/~adj/cs294-1.s98/wireless_lan/sld001.htmHow to start a Wireless ISP http://www.mikrotik.lv/3index.html#q1

Thank You!