The patents of telecom CDMA technology are in the hands of "baseband madman" Qualcomm, including 2G CDMA 1x and 3G CDMA EVDO. Although telecom 4G is not CDMA, if you want to make a phone call or send a text message, you still need to use CDMA network.
Besides producing SoC chips, another main source of profit for Qualcomm is baseband expenses. Every time a mobile phone manufacturer sells a telecom mobile phone, it has to pay a patent fee to Qualcomm.
Because this fee is calculated according to the baseband, if it is a dual telecom baseband, it will give Qualcomm twice the patent fee, which greatly increases the production cost of mobile phones. Telecom can't have dual cards at the same time because CDMA patents are too expensive.
Second, there is little demand for dual telecommunications.
The cost of dual telecom cards is high, but there are not many users of telecom mobile phone cards, and even fewer people need dual telecom cards. If mobile phone manufacturers produce dual telecom card mobile phones specifically for this small number of users, the final sales volume may be only tens of thousands, which is obviously not cost-effective from the profit point of view.
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Advantages of CDMA
CDMA mobile communication network is a combination of spread spectrum, multiple access, cellular networking and frequency reuse, including the coordination of three-dimensional signal processing in frequency domain, time domain and code domain.
Therefore, it has good anti-interference, anti-multipath fading and high security, and the same frequency can be reused in multiple cells, and a trade-off can be made between capacity and quality. These characteristics make CDMA have greater advantages than other systems.
1, with large system capacity.
Theoretically, under the condition of using the same frequency resources, the capacity of CDMA mobile network is 20 times larger than that of analog network, 10 times larger than that of analog network in practical use, and 4-5 times larger than that of GSM.
2. Flexible configuration of system capacity
In CDMA system, the increase of users is equivalent to the increase of background noise, which leads to the decline of voice quality. But there is no limit to the number of users, and operators can compromise between capacity and voice quality. In addition, multiple cells can be automatically balanced according to traffic and interference.
3. The call quality is better.
The channel structure of TDMA can only support a 4Kb speech encoder at most, but it cannot support a speech encoder above 8Kb. The structure of CDMA can support 13kb speech coder. Therefore, better call quality can be provided.
4. Simple frequency planning.
Users are distinguished by different sequence codes, so adjacent cells can use different CDMA carriers, and the network planning is flexible and the expansion is simple.
5. The network construction cost is low.
CDMA technology simplifies the planning of the whole system by using the same frequency in all parts of each cell, and reduces the number of required stations without reducing the traffic, thus reducing the deployment and operation costs.
CDMA network has large coverage, high system capacity and few base stations, which reduces the network construction cost.
References:
Pacific Computer Network-What is CDMA?