Equipped with much higher data speeds (potentially exceeding 100 Mbps), subscribers will benefit from access to a wider range of features and capabilities, which in turn allows telecom companies to generate more revenue from their customers. Market research firm Infonetics forecasts that by 2015, LTE subscribers will have surpassed 290 million, while ABI Research predicts that there will be approximately 600,000 base stations operating worldwide at that time. But even now, with the first deployments underway, Mike McHale of Livingston and Jonathan Borrill of Anritsu believe that serious questions remain about the technology and its viability.
Quality and Quantity:
According to a report by Infiniti Research, the global market for infrastructure supporting LTE mobile communications will be worth more than $11 billion in 2014. LTE represents a significant shift in the operation of mobile communications networks, moving to a fully IP-based topology instead of the circuit-switched topology used in previous generations of mobile telephony. This means that telecommunications companies must completely rethink how they assess Quality of Service (QoS). This will allow for end-to-end QoS monitoring, from the end user to the backbone network, since the headers for carrying QoS information are directly incorporated into the protocol stack. This will make it possible to prioritize data traffic transmission based on the service level agreement with the subscriber and the nature of the data (whether or not latency is a factor). As a result, new, more complex mechanisms will be obtained to measure QoS in terms of availability and continuity of service, and as a consequence, additional training for operators will be required.
A recently published forecast by industry analysts at iDate states that by 2020, annual global mobile communications traffic will reach an astounding 127 exabytes. The resulting congestion will be a true stress test for LTE network infrastructure. Telecom companies will need to utilize 40/100 Gigabit Ethernet to ensure that backhaul and access networks can handle this massive surge of data without compromising performance. This will require significant investment over the next few years.
Maintaining Coverage:
LTE will need to be deployed across different parts of the radio frequency (RF) spectrum for different geographic locations: 800 MHz plus 2600 MHz in Europe, 700 MHz plus 1900 MHz in North America, 2100 MHz in Japan, 2300 MHz in China, and 1800 MHz plus 2600 MHz in the rest of Asia. As a result, mobile phone manufacturers will have to develop models with multiple antennas to ensure users have global coverage. Consequently, compliance testing will be a considerably longer process than for previous generations of phones.
At the same time, more complex antenna configurations will be used in LTE deployments to support multiple-input multiple-output (MIMO) transmission. MIMO means that data throughput and mobile coverage can be improved without increasing bandwidth or transmission capacity because the signal is transmitted simultaneously over several different paths. This will require more sophisticated measurements by test engineers to calculate transmission speed. Previously, over-the-air (OTA) testing methods assumed that the achievable data rate was directly related to the received signal-to-noise ratio (SNR); furthermore, transmission range would improve with a line-of-sight transmission path. However, with MIMO, these basic rules no longer apply; therefore, technical personnel will need to be retrained.
Other concerns:
Since LTE networks will be deployed in stages to exploit areas with the strongest demand, cross-technology handovers between LTE and legacy 2.5/3G infrastructure will be constant. Consequently, telecom companies will need a wider variety of test equipment (to handle both old and new protocols), as well as a growing number of devices capable of handling both. GSM/UMTS and LTE likely offer similar coverage by using LTE's 800 MHz band. It is vital that the networks have good characteristics so that the telecom company can select the best network to provide the service requested by the user.
Passive intermodulation is another serious problem, which arises primarily when signals from base stations are affected by RF interference, which occurs when they mix with other wireless signals. This has been a concern with previous generations of mobile communications, but the resulting distortion is much more severe with LTE networks due to the high volume of data transmitted. In the case of passive intermodulation, more powerful testing equipment will again be needed to identify the source of the unwanted signals.
Finally, LTE technology requires a completely new strategy for planning mobile communications, one that pays particular attention to coverage maps and interference measurements. Through inter-cell interference cooperation (ICIC) mechanisms, it will be possible to verify that no adjacent cell uses the same subcarrier frequency in an overlapping area. However, currently, no LTE cells are operating in overlapping areas because they remain isolated from each other. Therefore, this is indeed uncharted territory. Only after activating a significant number of cells will it be known for certain how this actually works. Again, thorough testing will be essential to ensure proper configuration.
Clearly, from the various issues raised in this article, it can be concluded that the widespread implementation of LTE is not a foregone conclusion, despite what some may think. Those implementing LTE networks will need to acquire high-end testing equipment to perform the necessary modulation, bandwidth, and spectrum measurements. They will also need sufficient resources to analyze mobile coverage, conduct handover tests, and verify compliance with the protocol sequence and the protocols themselves. Therefore, telecommunications companies will have to coordinate closely with test equipment manufacturers and their suppliers to ensure they are prepared for the challenges they will face with LTE.
