By Robert Cifelli & Third Rail Wireless Broadband Solutions
Providers considering deploying a wireless broadband network for delivery of high-speed data and enhanced services often exhibit difficulty envisioning the scope of what the actual deployment entails. The goal of this paper is to provide a very general overview of what the process of deploying a broadband wireless system actually entails.
While wireless broadband networks are subject to the same technical considerations of traditional data networks, they also present an element of far more technical complexity. There are several key areas that are critically important to a successful broadband wireless network deployment. All must be taken very seriously to avoid the bulk of the pitfalls of poor execution. These areas are:
• RF Planning.
• Network Planning
• Equipment Selection
• Installation Planning
• Installation
• Security
• Maintenance
RF Planning
Unless you plan to operate in an unlicensed band you must first purchase or acquire frequency spectrum, which, in itself requires some RF planning. Getting the right number of channels with the proper separation requires knowledge of the equipment and the spectrum available. Sometimes it involves finding the right solution for spectrum in hand. The next part of RF planning involves laying out utilization of spectrum or frequency planning, selection of optimum transmission sites and system design for coverage of the customer base. Interference studies, link budgets and path loss calculations are necessary also.
Tools needed for these tasks include: Software for frequency planning, test equipment for field measurements and survey equipment such as a GPS and transit are all required. Trained personnel with experience designing and installing broadband networks and frequency planning are critically important. All of this work must be completed up front before the first piece of equipment is installed.
Broadband wireless data networks start out innocent enough but in time, if not properly designed and managed, can quickly become a nightmare of catch-up fire fighting and out of control growth. With proper network planning a network starts out considering its optimal load. Planning for expansion of the network must be done as forethought rather than an afterthought. Addressing schemes both private and public should be mapped out before the first subscriber is connected. Backhaul and interconnection schemes must facilitate offloading network traffic in a quick and efficient manner to allow the inherent buffering mechanisms in the network to smooth out speed differentials of on ramps and off ramps to the network.
Security is a chief concern among users as well as operators. All reasonable precautions must me taken to protect the operations center from inside and outside intrusion and to protect the users from each other. Just as in any other network that is connected by a shared medium, broadband wireless networks require security measures such as encryption, firewalls, virtual private networking, a managed network and managed services to minimize the risk of lost or stolen data. All of the traditional methods are employed on the data network sides of the install. The wireless domain security is facilitated by protocols and access control through modem registration that requires pre-configuration of the modem profile at the head end. Because we cannot be expected to secure the airwaves there has to be a security mechanism inherent in how the data is modulated and accessed to keep it from unintended eyes. Each vendor implements standard and/or proprietary mechanisms. Care must be taken to properly enable these mechanisms to the fullest extent allowable measuring risk against the overhead involved.
Evaluating broadband wireless equipment is not as simple as looking at a catalog and placing an order. There are licensed and unlicensed frequencies to operate in and many vendors specialize in equipment specific to each band. In the unlicensed bands there is greater risk due to the fact that there is no guarantee that the frequency you operate at without interference today will remain so for the future. In the licensed bands the risk of unauthorized interferers is significantly lower but the trade-off is the cost of the equipment is usually higher.
Generally, the unlicensed bands provide a cost effective solution for ISPs to compete with the LEC and CLEC. The cost of the licensed spectrum adds too much overhead to price-sensitive business models of ISPs. The LEC will prefer the licensed bands because it is easier to control and manage a resource that they own outright. In either case equipment selection needs to be based on the merits of the engineering and deployment success of the equipment and not just the promise of marketing collateral. An experienced advisor can be a valuable resource in this step of the process.
Having accurate maps with terrain data and sector/cell plot plans that are backed by path studies and frequency planning will help make the install proceed smoothly. The initial effort is divided between head end installation and key subscriber installs. The alignment of the head end equipment is critical because once bolted in place there is nothing to guide you or indicate where the physical boundaries between sectors lie. If there is as little as a one degree error in azimuth orientation of the base station all subscriber installs at the edges of the sector borders will experience intermittent or chronic problems that will be difficult to pinpoint because your base assumptions on sector/cell alignment are flawed.
A properly installed system is one that is balanced under operation. This means that transmit and receive gains across the board must be adjusted to be within the operating range of the gear, leaving room for fade margins and other anomalies of the RF world. A very important part of the installation planning is presetting the gains for the transmission equipment to within five percent of their expected final settings based on link budget figures. This is accomplished by making the whole system work on paper prior to turning the first screw.
Site readiness is multi-faceted. First you will have to assess rooftop access. In some cases the perfect mounting point for line of sight will not be accessible or of insufficient structural integrity. Second there must be sufficient power available and extended to the mounting site of the head end and cableway access at the subscriber antenna and radio mounting points. Power must be planned with backup and conditioning included. Weight and wind loading should be taken into consideration for rooftop and tower or mast mounting. Some systems place radio transmitters in a cabinet that is not integral to the antenna so there will be a need for a small room available in close proximity to the antenna mounting for housing the radio equipment. Proper and sufficient grounding, lightning protection, aesthetics, physical multi-path sources and physical security of equipment locations are considered during installation planning. A good plan for rollout ensures that you enjoy the speed to market deployment times promised by the technology. A flawed plan could stop the install in its tracks.
With all of the above steps completed and documented the install should be a simple matter of materials, logistics and personnel. Good seasoned install technicians led by experienced broadband wireless and network technicians can go about placing the base station and subscriber equipment according to the design constructed on paper. There must be a disciplined method of running cable, manufacturing finished cable ends, and measuring and adjusting receive and transmit power levels to make sure that the system remains balanced and error free. A computer network technician completes the installation at the head end by configuring the routers and at the subscriber end by configuring the client computer or router. Brief throughput testing is done to ensure that all is installed properly and that each added user did not degrade the network. It is good practice to initiate a quality control final inspection of physical connections and mounting integrity at the completion of each installation.
Physical security of the equipment involves taking reasonable precautions in site selection to avoid placing equipment within easy reach of passers by. In addition to that, access should be limited to only those who have a need for it. Equipment racks should be locked. At the subscriber sites equipment should be placed in a way that avoids the risk of accidental disconnect or incidental damage from moving or falling objects. This might sound like common sense to some but it is good practice to start and end an installation with a good look at what could cause problems with steps taken to mitigate them.
The question of data security comes up with every project. Because broadband wireless data networks are a relatively new technology it has been subject to all of the old and some new security questions and concerns. Each is addressed by planning. Designing an IP addressing scheme that facilitates management of the hardware and at the same time conserves public IP address space involves thorough knowledge of today’s routing protocols. Many of the first broadband wireless networks were designed as a flat switched environment but this soon became obsolete as the number of users soared past a few hundred. Today’s routers operate at wire speed and offer far more options for security than any layer two device (switch).
Security could be the subject of an entire paper on its own but here I will summarize by stating that it is important your integrator have routing and network design experts draft your network and security plans. In one sense it is like rocket science, if you launch without consulting experts, your network will crash soon after it leaves the ground. This point cannot be stressed enough.
Plan for periods of system maintenance rather than fixing just what is broken. Because the majority of the equipment is solid state electronics maintenance is a matter of software and firmware upgrades. These will generally take only seconds or at most a few minutes to accomplish but the down time must still be planned for so that it will not impact any service level agreements.
Network management falls under the maintenance umbrella and choosing the right tool for this task can be a daunting challenge. Element management packages take care of monitoring and configuring individual devices. They are very useful for quickly performing routine configuration tasks and gathering statistics on the device under observation. Network management must go deeper than this. In order to know what your network looks like and how healthy it is you must employ an Enterprise manager. Enterprise management packages monitor network performance and correlate alarms and events to probable causes and can take proactive action to route around trouble spots and outages. Help desk and trouble ticketing applications can be integrated with an Enterprise manager to give you a seamless network management platform. Problems are isolated quickly and resolved in a timely manner by giving all departments involved in network management a common communications and tracking mechanism.
A broadband wireless network is a hybrid network. The combination of RF and IP creates the need for hybrid engineering. It is essential that the RF part of the plant run flawlessly so that it is transparent to the IP engineering staff. It is also critical that the IP network be designed and managed for peak performance within the constraints of the RF mechanism as it evolves its way toward higher and higher bit-rates. Careful planning, thoughtful design and a good business plan are the cornerstones of a successful broadband wireless deployment.
About the Author
Robert Cifelli is Senior Solutions Architect with Third Rail Ltd. Third Rail is a vendor agnostic solutions provider specializing in the design, integration and installation of broadband wireless infrastructure and enhanced services. The author may be reached with question or comments at bob.cifelli@third-rail.net.