PRINCIPAL CLIENTS

12 Months Ended

Dec. 31, 2016

The following table represents revenue concentration of our principal clients:



	Year Ended December 31,
	2016				2015				2014
	Revenue		Percentage		Revenue		Percentage		Revenue		Percentage
T-Mobile	$	74,686	24.3	%	$	69,427	24.6	%	$	76,675	30.7	%
Sprint	$	45,137	14.7	%	$	25,422	9.0	%	$	—	—	%
AT&T	$	38,257	12.5	%	$	35,019	12.4	%	$	55,265	22.1	%
Comcast	$	25,323	8.2	%	$	31,976	11.3	%	$	40,868	16.3	%

We enter into master service agreements (MSAs) that cover all of our work for each client. These MSAs are typically multi-year contracts that include auto-renewal provisions. They typically do not include contractual minimum volumes and are generally terminable by the customer or us with prior written notice.

To limit credit risk, management performs periodic credit analyses and maintains allowances for uncollectible accounts as deemed necessary. Under certain circumstances, management may require clients to pre-pay for services. As of December 31, 2016, management believes reserves are appropriate and does not believe that any significant credit risk exists.

We have entered into factoring agreements with financial institutions to sell certain of our accounts receivable under non-recourse agreements. These transactions are accounted for as a reduction in accounts receivable because the agreements transfer effective control over and risk related to the receivables to the buyers. We do not service any factored accounts after the factoring has occurred. We utilize factoring arrangements as part of our financing for working capital. The aggregate gross amount factored under these agreements was $51,684, $33,980 and $26,376 for the years ended December 31, 2016, 2015 and 2014, respectively.