Switches are being replaced by routers en masse, but is the deployment and management of IP-based wireless networks really easier?

Internet protocol makes life easier. Is this a statement or a question? For me, it is a question. For the past few years as I have been working on various LTE projects around the world, including the new LTE-based nationwide public safety broadband network. I am hearing IT managers and professionals telling me how simple it is to deploy wireless networks now that everything will be IP-based end-to-end. Gone will be the switches, replaced by routers. But is developing IP-based wireless systems really less complex and easier?

The answer to this question depends on who you are and your job responsibility. There is a transition taking place around the world. Radio experts are finding that they are being replaced in some areas by people with IP experience and IT departments are being given the overall management responsibility for establishing wireless networks and keeping them running. I, for one, am not at all sure that this move to IT systems managers is entirely a good thing. I have discussed wireless with many of them and they tell me that as far as they are concerned, the new IP-based networks are simply more IP pipes for them to deploy and use. 

But designing a wireless network, IP or not, requires a lot more than an understanding of IP and traditional IP training and experience. Radio engineers are still a very important part of the network planning and build-out, even more. When we moved to 3G and now 4G systems (with the exception of some WiMAX systems), spectrum utilization became what is known as 1:1. That means that each macrocell, microcell, picocell, and femtocell reuses the same spectrum that is used in the cell sites adjacent to them. If the systems are not engineered correctly from the perspective of radio coverage and site coverage overlap, there will be interference between cells or cell sectors, which will reduce both the coverage and capacity of the network. 

Future releases of LTE from the 3GPP will include technology designed to make the networks “self-healing” and self-configuring. While that might help mitigate some of the interference issues, it does not and will not mitigate all of them. Typically, networks are built out using fewer sites to start with and then additional sites are inserted to fill in coverage and add capacity where needed. Wireless networks are not simply built, optimized and then left alone. Every network operator is constantly tweaking and expanding them, filling in holes and adding new sites for more capacity and better in-building coverage. This takes talented radio engineers schooled in radio technology, but more than that, it takes radio engineers who have field experience. 

In the early days of two-way radio, we usually designed a system by calculating the coverage it would provide using formulas and acquired practical knowledge. Today, we sit down in front of a computer and plug a number of parameters into a program designed to calculate coverage and show us where coverage can be expected and where the signals will be blocked by terrain, buildings and the like. 

However, these predictive programs only give us an approximation of the coverage we can expect. True coverage can only be determined after the site is built and after actual drive testing. Once the actual coverage is known, some changes can be made to the site’s coverage by changing out the antennas, using fixed or electrical down-tilt to adjust a pattern, and other tricks of the trade. The bottom line is that each cell site has to be built, inserted into the network and then tweaked until it fits in and the interference between it and the other sites is minimized. 

Once the hardware has been installed and tweaked for best performance, it is then integrated into the network and this is where the IT folks take over. Network settings have to be optimized so that handoffs from one site to another are seamless. In LTE, this is a fairly complex issue and if one site has equipment made by one vendor and the next site has equipment made by another, the hand-off configuration usually has to be different from handing off between sites that have the same hardware. 

There have been a number of notable network failures recently. The latest was the T-Mobile failure of the data portion of its network. Verizon has also experienced multiple failures on its LTE network over the past couple years, and others have as well. It is interesting to note that these failures have not been related to the radio portions of the networks but rather, in most cases, the back-end computers and routers. Behind most LTE systems is a complex IP-based system known as IMS, or IP Multimedia Subsystem. This is the heart of the network and, like all computer-based systems, the interaction of the hardware and software is critical to its operation. Something as simple as a systemwide software upgrade to the network can cause outages, either on a nationwide basis or in portions of the network. 

LTE stands for Long Term Evolution and the 3GPP standards body and others are busy on new releases of the specifications that must then be interpreted by the vendors and converted into code for the various networks. To make this even more difficult, not every network operator has, or will, implement all of the various new capabilities and features provided in the new standard. Thus, the coding has to be based not only on the 3GPP standard, it has to include only the features and functions that the network operator wants to implement. As we move forward into this world of RF transport and IP back-end systems, we will experience more glitches. That is the nature of the beast. 

As any programmer knows, it is usually more difficult to troubleshoot a software program than it is a piece of hardware, especially since two programmers can view the same code and have different ideas about how to “fix” or enhance it. We have come a long way with wireless broadband, but I contend that it is not less complex than the older systems; rather, it is more complex with more chances for failures along the way. Radio frequency design and coverage is part science and part black magic. The black magic part is what is handed down from experienced field engineers who have been there and done that! Today’s new IP-based wireless networks also seem to be part science and part black magic.

Those savvy in the world of radio frequency and those savvy in the world of IP live in different worlds. As we move ahead, there must be some cross training of these two non-exact sciences if we are to build robust, functional wireless broadband networks. Even so, there will continue to be glitches, which is one reason that I never rely on a single means of access to either my data or the Internet.