When wireless carriers first started relying more heavily on packet networks for backhaul connectivity, they also realized they would need a new approach to providing synchronization for backhaul networks. Initially attention focused primarily on an option known as Sync-E that is built into network devices and on IEEE (News - Alert) standard 1588v2, also known as precision timing protocol (PTP), which is based on a separate message stream running over the operator’s network. But, one synchronization expert sees some other options in the running, especially now that the wireless industry is putting so much attention on small cells aimed at enhancing network capacity in high-traffic areas.
“From a synchronization standpoint, small cells have to meet 3GPP specifications for frequency and phase response,” said Manish Gupta (News - Alert), vice president of marketing and business development for Symmetricom, in an interview. Unless a small cell meets those specifications, carriers will find that they can’t do call handoffs, that video will be jittery, that location-based technology is not accurate and that spectrum efficiency will suffer, Gupta said.
Symmetricom (News - Alert) specializes in network synchronization and this week announced new timing and synchronization software designed specifically for embedding in small cell equipment. The company is offering both residential and enterprise versions of the software and along with these new offerings comes at least one acronym that may be unfamiliar to some readers – network timing protocol (NTP), which is the same technology that is used for the clock that is built into your computer.
Interestingly Gupta doesn’t see Sync-E playing a role in synchronization solutions for small cells because the connection to the small cell may lack the Ethernet capability required for Sync-E. A residential small cell, for example, typically relies on a DSL or cable modem connection.
As Gupta explained, small cells fall into one of three categories – including metro, enterprise and residential – and each of these categories have different requirements regarding frequency stability measured in parts per billion (ppb). While the requirement for a residential small cell is 250 ppb, enterprise small cells must meet a more demanding 100-ppb standard and metro small cells have an even more exacting requirement of 50 ppb.
Also impacting synchronization requirements are phase synchronization requirements, which are particularly stringent for some forms of LTE (News - Alert) networks.
Symmetricom believes the synchronization requirements for residential small cells can be met by using NTP or a combination of NTP and global positioning system (GPS). NTP can play an important role when used with GPS because it helps overcome an important limitation of GPS-based timing – the difficulty of gaining information from GPS satellites from an indoor location.
NTP “makes GPS [more] sensitive so that even indoors you can latch onto a signal,” said Gupta.
For enterprise and metro small cells, however, Symmetricom recommends synchronization based on PTP and GPS. The reason is that PTP is better able to support the higher frequency stability required for those applications, as well as the stringent phase synchronization requirements of LTE, the company says.
I asked Gupta how wireless carriers have addressed synchronization requirements for small cells up to now and he said they have focused on home grown solutions or solutions developed for enterprise networks that are not carrier grade. As small cells are deployed more heavily, he expects carriers to insist on carrier-grade solutions.
Want to learn more about the impact and potential future of White Spaces? Then be sure to attend the Super Wi-Fi Summit, collocated with ITEXPO West 2012 taking place Oct. 2-5 2012, in Austin, TX. Co-sponsored by TMC (News - Alert) Partner Crossfire Media the Super Wi-Fi Summit will address the opportunities, challenges and technical issues surrounding the use of White Spaces for wireless broadband services. The event will cover all aspects of the White Spaces market including, results and next steps for recent technical trials, White Spaces backhaul opportunities, database issues, White Spaces Devices, Spectrum (News - Alert) Issues, Standards and more. For more information on registering for the Super Wi-Fi Summit click here.
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