Spectrum bands typically dictate the technology that can be used.
Licensed Spectrum refers to frequency bands reserved by a country’s telecommunications regulatory body (CA for Kenya, ICASA for South Africa) for use by certain companies like television and radio broadcasters, cellular network operators, etc. These frequencies are auctioned at a fee. Licensed bands allow their users to manage performance more efficiently, enabling them to take advantage of lower noise levels therefore they are assured of no interference.
Lightly-Licensed Spectrum also known as managed spectrum is shared with other users but can be managed either through a fixed database where users input their information or through a spectrum manager on a real-time basis. They are non-exclusive licenses at a lower cost. In Kenya, Communications Authority (CA) has adopted a lightly licensed model of service for TV White Space (TVWS) applications.
Unlicensed Spectrum, also known as license-exempt spectrum is a part of the electromagnetic spectrum that can be assigned to or used by anyone for non-exclusive usage. This includes the 2.4GHz and the 5GHz band. Even though this band is free, users have to adhere to existing constraints limiting power levels of equipment used, what we call type-approval. Here, you will find Wi-Fi, Bluetooth devices, baby monitors, wireless microphones, and other technologies, and so as expected, technology using unlicensed frequency bands is prone to interference. Kenya recently adopted the 6GHz band popularly known as WiFi 6E. Unlicensed spectrum is used for technologies such as WiFi, Bluetooth, microwave, garage doors, baby monitors, and some IoT devices. Community networks make use of unlicensed spectrum.
Current regulations in Kenya do not require Wi-Fi devices in 2.4 GHz and 5 GHz to have a unique national type approval but must comply with the maximum permitted output powers specified for each band. The primary differences in the wireless frequencies are the range (coverage) and bandwidth (speed) that the bands provide. The higher the frequencies, the lower the penetration rate, however, the higher the frequencies, the higher the data transmission rate.
The 2.4 GHz band provides the most coverage but transmits data at slower speeds. It has a long-range, and better obstacle penetration. Because it is used by most devices and has only 3 channels, it is most prone to interference.
The 5 GHz band provides less coverage but transmits data at faster speeds. It has a short-range, and can’t easily penetrate solid objects meaning when using a 5GHz device and you move to another room in your house, the connection might drop. It has 23 non-overlapping channels and therefore offers almost 8X as much capacity as the 3-channel 2.4 GHz band, meaning it is less prone to interference.
The 6 GHz band, introduced with the new WiFi 6E standard, provides the least coverage but transmits data at the fastest speeds of the three frequencies. It is exclusive to devices that support WiFi 6E. The 6 GHz band also supports almost twice as many channels as the 5 GHz band. Fewer devices, more spectrum, and more bandwidth mean less interference and network congestion. Kenya recently adopted the 6GHz band in the 5925-6425 MHz band for license-exempt use in line with the African Telecommunications Union’s July 2021 recommendation.
Interference is one of the major shortfalls of the license-exempt spectrum; users have no right of non-interference and no right to cause interference. Unlicensed spectrum is prone to interference either due to congestion of devices in one geographical area or from other paying Wireless Internet Service providers (WISP) because unlike licensed spectrum, unlicensed spectrum is not protected. Licensed spectrum holders have the right to involve the authorities in removing the interfering party or parties from the licensed area.
Managing interference between adjacent users in an unlicensed spectrum can be achieved through various ways:
It can be done using the following strategies:-
- Reducing transmitting power – Adaptive Power Control (APC) Static or dynamic power control is an effective method to control interference, where a radio transmitter automatically minimizes the transmit power necessary for effective communication. This ensures that radio waves die out quickly before colliding with adjacent users.
- Use higher frequency bands – Radio waves traveling at higher frequency bands die much faster compared with those traveling at lower frequency bands. Kenya recently adopted the 6GHz band in the 5925-6425 MHz band for license-exempt use. There are fewer devices using this band, more spectrum, and more bandwidth which means less interference and network congestion.
- Use frequency hopping – This can be done using frequency Hop Spread Spectrum (FHSS) and AdaptiveFrequency Hopping (AFH) Used in FHSS (Frequency Hop Spread Spectrum) systems. According to a resource on unlicensed devices & spectrum by ITU, FHSS systems distribute energy over the spectrum by hopping across different frequencies during a transmission, which makes the system more immune to narrow-band interference.
- Frequency Agile Systems – Many RF communications systems are “frequency agile” in that they can be reconfigured to operate on an alternative frequency. In contrast to frequency hop systems, frequency agile systems generally remain on a single channel for a sustained period of time.
- Use of TV white Space Spectrum to increase the spectrum options for Community Networks
Community Networks use devices that rely on the unlicensed spectrum bands 2.4 and 5 GHZ ranges, susceptible to interference. Cheaper access points normally lack good noise management capabilities. As the number of users in the population grows ,interference increases. We have access points and antennae with good noise management capabilities using the above technologies but they are expensive and beyond the reach of most Community networks. Even if the Community networks can afford them, it takes a long time to recoup any money invested in the Infrastructure.
This is a series of blogs about Spectrum in a series of our publications on Community Networks.
Ms Catherine Kyalo is the KICTANet Africa Regional Coordinator for Community Networks under the APC-LOCNET initiative. She is passionate about community welfare and enjoys yoga to rejuvenate. LinkedIn | Twitter