In the hunt for new ways to handle growing data volumes, NTT DoCoMo and Huawei Technologies have demonstrated that LTE can be deployed over 5GHz, which today is used for Wi-Fi networks.
One of the ways mobile operators can boost capacity in their networks is to increase the amount of spectrum, which could be compared to adding more lanes to a highway. The 5GHz band is one alternative they and other vendors have started to look closer at.
The indoor test found that LTE can work in the 5GHz band at speeds of up to 100Mbps, DoCoMo said via email. The test showed so-called LAA (Licensed-Assisted Access) can be used to enhance current LTE networks, and also networks based on LTE-Advanced. The plan is to use LTE at 5GHz alongside Wi-Fi networks to improve capacity using small base stations or cells, a scenario where it shows "great potential," according to DoCoMo.
Today's mobile networks use licensed spectrum, which operators are granted access to by local telecom authorities for a fee. Unlicensed spectrum is free for anyone to use as long as they stay within rules for operating in the band. The lower cost is the upside, while unpredictable performance is the drawback.
DoCoMo, Huawei and other companies such as Alcatel-Lucent, Nokia and Qualcomm are looking at using unlicensed spectrum for just download traffic or for download and upload traffic. Another alternative is to combine the two spectrum types using carrier aggregation, which is the most important LTE-Advanced feature. It allows networks to devote more resources to some users by treating two or more channels in the same or different frequency bands as if they were one.
But not everyone is convinced LTE needs to be rolled out in unlicensed spectrum bands.
"Those places where LTE would be available, people use Wi-Fi anyway. From a consumer perspective what it would allow you to do is to use the operator's core communication services, such as telephony and messaging. Beyond that, people are now so used to using Wi-Fi that it won't be hugely different," said Mark Newman, chief research officer at market research company Ovum.
Some mobile operators are looking at using Wi-Fi for calls and SMS, which would remove that advantage for cellular networks. British operator EE will launch the capability later this fall. Calls will be made through the phone's native dialler, with no need to rely on an app, it said in June.
In general, Wi-Fi is becoming more tightly integrated with cellular networks, according to Newman.
The work on using LTE in unlicensed spectrum such as the 5GHz band is still in its infancy, and even though DoCoMo thinks the technology looks promising it doesn't have a solid plan to commercialize it at the moment.
"Currently, we are aiming to finish the joint experiment by fiscal 2015. The next step will be to develop a technology that will enable LAA and WLAN to efficiently coexist in the same spectrum. We hope LAA will be standardized with the Release 13 LTE which should come out in fiscal 2016," DoCoMo said.
The operator's fiscal year ends in March every year.
