On March 29, 2016, the Federal Communications Commission (FCC) started an auction process for new wireless service licences in the 600 MHz band. What does it mean for the Broadband Cable Operators? Well, put bluntly, this will add another 100 MHz of potential LTE ingress interference on the broadband cable plant.
Let’s consider the power levels involved in LTE transmission. The typical effective radiated power (ERP) output of a cell tower is about 1.5 kWatts. A 1.5 kW ERP corresponds to +62 dBm. Once we convert this into radiated field strength, the cell tower will radiate a signal of 218 V/m @1m or 7 V/m @30m. The typical effective radiated power (ERP) of a cell phone is 0.2 watts, which corresponds to +23 dBm. Once we convert this into radiated field strength, the cell phone will radiate a signal of 2.45 V/m @1m or 0.082 V/m @30m.
A Motorola white paper on shielding effectiveness (SE) indicated that a high-quality well- terminated cable drop will exhibit sufficient SE to prevent interference in fields greater than 10 volts per meter (V/m). The same paper concluded that an SE value of 100 dB corresponds to the value needed for the threshold interference for 256 QAM DTV signals at the minimum FCC required level of -12 dBmV at an applied field of 1 V/m.
While operators have relatively good control over the external plant in relation to its SE, it could be quite a different story on the customer’s site. Some customers will add a TV set or wire a newly constructed room using ‟non-professional” passive equipment, such as splitters, terminated coaxial cables, etc. In the Motorola paper, it was demonstrated that SE could differ as much as 50 dB, between the cable operator’s professionally installed passive equipment (coaxial drop and splitters) and the same type of passive equipment of a lower build quality purchased and installed by the client.
So how do we fight back regarding these LTE interferences? The first step would be for you to use the best quality passive equipment to increase your plant’s SE. Check whether your cable installation procedure has been correctly applied by your staff and contractors. The operator’s staff should discard any passive equipment not provided by the company, since this equipment will likely have insufficient SE against LTE interferences. Once a cable installation or service call has been completed, add a proactive step to your service procedure by performing a ‟leakage pressure test” to ensure there is no cable leakage present. A leakage pressure test is conducted by applying a high RF level set of carriers at the drop input. While using a cable leakage receiver, your staff will walk through each room on the customer’s premises to make sure that there are no leaks present before they leave, thus avoiding a potential truck roll.
Image: CPAT DRV3 Lite Dual-Band Cable Leakage Receiver
Controlled quality installations will become even more important with the additional LTE spectrum falling directly into the broadband cable spectrum. Increasing shielding effectiveness across the plant by using a preventive maintenance program, and adding a quality installation control process while your staff is on the customer’s premises is a proactive step to help diminish the impact of LTE interferences on your cable plant.
Do you want to learn more about solutions specific to broadband cable operators? Contact Effigis and receive a customized solution for your project.