CDMA450 - CDMA at 450 MHz
- basics of CDMA450 or CDMA 450 versions of CDMA2000 1X and 1X EV-DO used in the 450 MHz cellular band.
CDMA450 is a form of CDMA2000 that operates across the 410 - 470 MHz cellular band. This band is often referred to as the 450 MHz band, and this gives rise to the name, CDMA450.
The CDG - CDMA Development Group state that CDMA450 is the only 3G (IMT-2000) solution that is commercially available for deployment in the 450 MHz frequency band.
CDMA450 is a generic name for all the CDMA systems that use the 450 MHz band - all the standards published by the TIA as TIA-EIA-IS-CDMA2000. As such, the CDMA450 system includes the following CDMA systems:
- CDMA2000 1X
- 1X EV-DO Release 0
- 1X EV-DO Revision A
- 1X EV-DO Revision B
- Any future enhancements to these technologies
Often the CDMA2000 1X and EV-DO services run alongside each other, but using different carriers. In this way both voice and data services can be delivered.
CDMA450 propagation advantage
One of the major factors of CDMA450 is that it uses the 450 MHz cellular band. At these frequencies a greater level of coverage can be achieved from a single base station. This means that it can achieve the same coverage utilising less base station than a system using higher frequencies. This makes CDMA450 ideal for rural areas where wide area coverage is needed.
However the same attributes are not so useful in densely populated areas where increased data capacity is needed and small cell sizes are needed to provide this.
Within the cellular industry there is a rule of thumb that for every doubling in frequency, around three to four times the number of base stations is needed to provide the same coverage.
Similarly the range provided by each base station is reduced. A rough calculation indicates that at 450 MHz a base station might provide a range of 50km. The same station at 850 MHz would have a range of around 30km, and at 1900 MHz this would be around 13km.
The 450 MHz band includes sub-bands in the frequency ranges of 410-430 MHz, 450-470 MHz and 470-490 MHz.
CDMA 450 multiband and multimode
In view of the features of CDMA450, and its deployment, a number of networks rely on the CDMA450 elements to provide the wide area coverage. Accordingly a number of systems will utilise CDMA450 / CDMA800 phones, etc. - others may even require handover / handoff to completely different radio access networks such as GSM or UMTS, etc.
While spectrum is not available for CDMA 450 in all countries, it is nevertheless deployed in many areas around the globe. Often it is used to provide mobile broadband, especially in rural areas. In addition to this many operators are asking for CDMA450 systems to be maintained until at least 2021, so it is likely to remain in use for many years.
By Ian Poole
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