In 2016, the total Diameter Signaling Controller market, including both product and service revenues, increased 33% versus 2015 to $748 M. Service revenues grew 32% over the same timeframe and accounted for 32% of the total market. Product revenues grew 34% for the year as a 45% increase in Tps shipments was partially offset by an 8% decline in the average selling price per Tps. In 2H16, the total DSC market, grew just 7% compared to 1H16 but was up 34% versus 2H15 to $387 M. We expected that seasonal factors plus the continued transition to LTE and VoLTE would drive the market to even higher growth rates, but in 2H15, this was not the case. We believe that the less than expected revenues in 2H15 was due to timing factors and that the market remains poised for sustained long- term growth.
We forecast that in 2017 the total market (product and services) will grow by 53% to reach $1.1 B as LTE and VoLTE deployments—and subscriptions—continue to grow. At the end of 2016 LTE subscriptions stood at 1.7 billion or 23% of the worldwide total so we believe that the DSC market will have a very long and large growth potential. We forecast that in 2021, LTE subscriptions will amount to 4.2 B still just 48% of the worldwide total so the DSC market should continue to be a vital one for the coming decade. Similarly, since 2G and 3G subscriptions still account for approximately 77% of global subscriptions, the SS7/STP market remains substantial and continues to see good investment from operators who are increasingly considering converged signaling solutions that incorporate both DSC and IP STP functionality. SS7 security concerns are also prompting new investment that incorporate firewall functionality into the IP STP. We are forecasting that the total DSC market (product plus service revenues) will grow by a CAGR of 23% through 2021 to reach $2.1 B, which is consistent with our previous forecast.