Why Sprint Nextel has more dropped calls than its competitors AT&T and Verizon?

Hello all,

Sprint Nextel is a company that has been on a revival for quite some time. The market has been responding positively to the radical steps taken by Sprint to create a niche for itself in the telecom market. The customer service has been improving over the past few months, a positive vibe is being created in the market about the improvements in the customer service and the network reception. Thanks to the new CEO Dan Hesse for re-vamping the company and prioritizing these major issues to be addressed. 

One major issue Sprint Customers always faced is the "Higher Dropped Calls Rate". 

Why does Sprint have more dropped calls than its competitors AT&T and Verizon?

This is the topic of my blog and I will be explaining the reasons for this higher dropped call percentage. 

First of all, let me tell you some facts about these three major wireless carriers. 

Verizon uses CDMA (Code Division Multiple Access) technology and operates in the 800 MHzfrequency range. 

AT&T uses TDMA (Time Division Multiple Access) technology and operates in the 800 MHzfrequency range.

Sprint uses CDMA technology and operates in the 1900 MHz frequency range.

Verizon and Sprint use the CDMA technology while AT&T uses the TDMA technology. Each of these technologies have their own advantages and disadvantages, and we are not going into the details of these technologies as they are not responsible for the drop calls, which is the topic of this blog. The next major observation you might have made is in the frequency range in which these carriers operate. Both AT&T and Verizon operate at 800 MHz frequency and Sprint operates at 1900 MHz frequency. Why am I discussing this point? Are you thinking this is the reason for the increased dropped calls on the Sprint Network? If you are thinking that way, you are right on target. Yes the frequency of operation is the major reason for the dropped calls. 

Let me explain in detail why this is a valid reason.

Any wireless signal propagating in the free space follows something called as free space path loss to determine the power of the signal at the receiver.

P_r = P_t G_t G_r ( λ / 4πd )² 

This is the equation which gives the power of the received signal at the receiver, where Pt is the transmitted power. For more detailed explanation please refer to this page.

As you can see the received power at the receiver is directly proportional to the square of the wavelength of the transmitted signal carrier. As frequency is inversely proportional to the wavelength, lower the frequencies => higher the wavelength and therefore, higher received power. You can clearly observe the decrease in the receiving power as the frequency increases in the table given in the following page. So as the frequency of the signal increases the coverage area of the transmitting antenna reduces. This is exactly the problem faced by Sprint. As you can observe the frequency at which Sprint operates (1900 MHz) is higher than the frequency at which both AT&T and Verizon operate (800 MHz) and as the transmission power of a cell tower is restricted by the FCC regulations, the coverage area of Sprint tower would be lesser than the coverage area of AT&T or Verizon tower. So in order to cover the same area, Sprint needs more transmitting antennas at higher operating frequencies than its competitors operating at lower frequencies.

Easiest thing for us to say is, “why doesn’t Sprint install additional antennas to compensate for the higher frequency range and lower coverage area?” Well Sprint did deploy additional towers everywhere throughout the nation and took extra care to make sure the customers have very less to no dropped calls but in spite of the effort, the network is failing to deliver the results as the higher frequencies are more vulnerable to the surroundings than the lower frequencies. Trees around the cell phone might make the signal weak, black paint can make the signal weak, and there are many other factors that can impact the power of the signal. This creates a lot of holes in the network. This is the reason for increased dropped calls when you are travelling from one location to another.

Another phenomenon called diffraction helps the wireless signal to bend around an obstacle’s edge and reach the receiver. Sprint’s higher frequencies fail to impress in this phenomenon too, as the performance of signal undergoing diffraction is better at lower frequencies than at higher frequencies. The signal bends around the edge of the obstacle better at lower frequencies than at higher frequencies.

Penetration is another phenomenon by which the signal reaches the receiver (cell phone) when you are indoors. Even in the phenomenon, Sprint’s higher frequencies perform badly than its competitors. As the signal penetrates through various obstacles it is attenuated (amplitude reduces as it passes through the walls) and as the frequency increases the rate of attenuation increases, thereby making the signal weak indoors. For additional clarification or explanation of the process please refer to the following white paper.

Finally, these are the reasons for Sprint’s higher drop call rate and lack of signal indoors. You might be wondering, why Sprint chose these higher frequencies when there are so many disadvantages associated with the frequency range? Well that’s a valid question and there is a substantial reason for this selection. I would be discussing the reasons and advantages of selecting this higher frequency range in my later blogs.

Currently Sprint is making an intriguing effort to fill the holes in the network and provide spotless network to its customers by using various technologies like using a broadcaster at home to pull the signals and re-broadcast them in the house, using these repeaters in places of reported signal lose etc. Will it be successful in changing the image that the customers currently have? We have to wait and see.

Thanks a lot for reading my blog. Feel free to leave comments on this discussion or also feel free to email me any questions you might have on the following discussions.

References:

1. http://www.crouse-hinds.com/wirelessIO/PDF/White%20Paper/white_paper_frequencies.pdf

2. http://www.dsprelated.com/showarticle/62.php

3. http://www.fcc.gov/pshs/techtopics/techtopics17.html

Sincerely,

Krishna Chaitanya Emani.