As telecom operators look for increasing capacity and coverage of their network while at the same time – controlling their CapEx – Distributed Antenna System or DAS is a great way to address the growing needs of telecom customers. Montreal, Canada based iBwave is powering global innovations in the field of in-building wireless network design and creating unique value propositions for its customers.
Vladan Jevremovic, PhD, Research Director, iBwave speaks with Zia Askari from TelecomDrive.com about the way DAS segment is evolving ahead and why NFV is important for the industry today.
How DAS has as a technology changed over the years – and where is it moving now?
DAS started out as a purely passive network. An RF signal coming from a nearby BTS sector, captured by a highly directional Yagi antenna, would be sent via coaxial cable to a telecom close and amplified by an RF repeater. From the repeater, the signal would be distributed via in-building network to multiple indoor antennas located throughout the building. At the time, the distribution network consisted of coaxial cables and RF splitters. The size of first generation passive DAS networks was limited by excessive coax cable loss, of the order of 3 dB/100 ft (10 dB/100 meters).
The second generation DAS overcame this problem by converting RF signal to optical signal. As fiber cables have a very small loss (0.6 dB/mile), the signal could reach greater distances throughout a building once signal from RF source was converted to optical. At the indoor antenna end, optical signal needed to be converted back to RF and amplified.
These remote end amplifiers are called “Remote Units”, (RU) and since amplifiers are active elements, these DAS networks are called “active” DAS networks. The presence of RUs allows active DAS RF signal to be more evenly distributed throughout the venue than a signal from passive DAS. However, RUs also make active DAS more expensive, so in order to reduce the cost, some DAS architectures have coaxial cables and RF splitters between an RU and multiple indoor antennas. It is important to point out that coaxial cable is a single use media used for mobile network throughout the building, as WiFi and Ethernet are not included.
Second generation hybridfiber/coax DAS is mostly deployed in large public venues, where wireless operators share the DAS infrastructure, thus driving the deployment cost per operator down. As the second generation DAS matured, primary use case moved from RF coverage enhancement to capacity enhancement, so Base Stations replaced RF repeaters as RF signal source.
As subscribers used more and more data, big public venues oftentimes required tens of Base Stations to be collocated at the DAS headend. This is a housing problem at the headend, and oftentimes, a separate structure near a stadium needs to be built specifically for the headend. This, in turn, further increases the cost of DAS deployment.
DAS is currently evolving to a third generation, all optical DAS architecture that pushes fiber to the edge of the DAS network. Third generation DAS Remote Units have integrated antennas, thus eliminating passive network between RU and antenna and providing 1:1 antenna granularity. This allows for better uplink S/N ratio, which improves uplink data rates and enables better network optimization function.
An all fiber network makes a unified platform for passive optical LAN, cellular and WiFi a reality, which gives end user complete access to broadband. In addition, as fiber provides virtually unlimited bandwidth, it can also support vertical specific applications over the same fiber reach infrastructure, like medical telemetry, IP surveillance camera TV, public safety…
At a time when telecom operators are looking for alternative ways to augment their network reach and capacity at a minimum cost – how can next generation DAS solutions help?
A recent development of digital interface between DAS, and Base Station reduces the cost of HeadEnd deployment. If a licensing agreement with a BTS OEM is in place, a centralized pool of BTS Base Band Units (BBU) can be directly connected to DAS HeadEnd, thus eliminating a need for BTS RRH, which saves energy and real estate. In a use case where multiple venues (stadium, hotel, shopping center) are connected to the DAS, pooled BBUs can be reassigned between the venues, according to their unique traffic patterns. As an example, a shopping mall may get most pooled resources during the day, hotel gets the most at night, and stadium gets the most during sporting events on weekends.
DAS monitoring also benefits from an all digital DAS. Identifying the source of PIM in large neutral host hybrid fiber/coax DAS is a labor intensive process. Even ifdiagnostic software can pinpoint an RU as PIM source, each antenna connection at the RU still has to be inspected manually. In digital DAS, coax network is eliminated, and the PIM source can be identified at antenna directly. Similar benefits are realized in DAS commissioning as well.
What are some of the big innovations that are likely to come from your organization in this direction?
We remain very close to our customers in order to really understand their needs and processes, and from there we find innovative ways to streamline & simplify their tasks to save them time and money. This motivation is deeply ingrained in our DNA and forms the basis for continued innovation. Integrating third party tools and systems to the iBwave platform in order to provide a more compelling end-to-end value for our customers is just one example of the type of innovation for which we strive for.
What is the impact of fast emergence of NVF and SDN in the telecoms space – on the DAS ecosystems?
Mobile operators deploy Radio Access Node (RAN) architecture with functions distributed into 2 network elements: a BaseBand Unit (BBU) which performs the processing of the radio protocols and Remote Radio Head (RRH) which converts digital signal coming from BBU into the analog signal for transmission and reception. The RRH is connected to the BBU over a digital link that needs to support very high bit rate, upwards of 1 Gb/s.
Network Virtualization Function (NFV) of RAN architecture leverages IT virtualization technology to realize at least a part of RAN nodes onto standard IT servers, storages and switches. NFV is expected to provide dynamic resource allocation, traffic load balancing, easier management and operation and faster time to market. In Centralized RAN (C-RAN) BBUs are separated from the RRHs to the cloud for centralized processing and capacity management. For data and channel information to be shared among a pool BBUs,high bandwidth and low latency interconnection must be supported, making fiber links prime candidate for the transport media.
Digital DAS provides architecture to support virtualization of RAN architecture. Digital DAS Fiber optical connectivity from BBU pool all the way to remote antenna is capable of supporting necessary digitized signal bit rates, using Ethernet, CIPRI, OBSAI or ORI interface. Digital DAS can also carry signals of multiple wireless operators over a common infrastructure, thus enabling effective cost sharing. Adding digital Ethernet backhaul over a common infrastructure providesa unified platform for broadband services in a building, including passive optical LAN, small cells and WiFi. While NFV and Centralized RAN lower total cost of ownership for a wireless operator network, Digital DAS lowers the total cost of ownership ofa neutral host DAS, making it more appealing not only for public venues, but also for Enterprise markets, such as healthcare, hospitality, education, etc.
What are some of the global geographies that iBwave is targeting today?
iBwave has a global presence with more than 800 customers in 90 countries. We are growing fast in all geographic areas where 4G is being deployed to satisfy exponential indoor data demand. Our software solutions help customers worldwide realize the full value of wireless voice and data networks, increasing competitiveness by improving the user experience, reducing churn and generating revenue through data applications to maintain ARPU. Our in-building software solutions optimize capital expenditure and let the network live up to its full potential.
How do you look at the emerging markets of India and the neighboring countries? please share your plan for these regions?
India is one of the fastest growing major telecom markets in the world with a global middle class that is growing steadily and a smartphone market that is soaring. All this combined with new shopping malls, airports, office buildings and hotels is triggering an indoor data demand boom that can only be satisfied by deploying 4G networks and small cells.
iBwave is the undisputed in-building design and planning leading company in India, we are helping Indian wireless operators, system integrators and equipment manufacturers bring strong, reliable voice and data wireless communications indoors, profitably.