In the in-building DAS connectivity world, progress is often viewed through the lens of enabling pervasive data connectivity for all employees working in a particular building at a given time. However, the impact of smart buildings and Internet of Things (IoT) in general, will have a potentially greater impact on in-building networking requirements going forward.

Although many building owners are starting to view the quality of their in-building cellular network as a fundamental facility, there is still a sizable sentiment within the commercial real estate industry that connectivity is a tenant and/or cellular service provider issue. As the Internet of Things (IoT) continues to proliferate, properties that do not have an adequate in-building network infrastructure to support applications and services in the 5G era will find it difficult to compete for tenants. Naturally, no one in the real estate ecosystem wants this to happen.  As the next phase of in-building wireless connectivity unfolds, below are few recommendations to help support new and/or ongoing deployments.

Large venues: Despite the fact that most airports, large malls, and entertainment venues have at least partial DAS installations and some level of public Wi-Fi connectivity, owners of these properties must take the next step. This includes becoming more aggressive deploying complete DAS networks that will offer a migration path to 5G. It also means working with an ecosystem of partners that will help deliver a premium experience to attendees.

Neutral Host investment models are needed: Although large, marquee venues can often attract a major wireless carrier to lead investments into DAS and other in-building connectivity solutions; there is a quick drop off in carrier willingness to invest in venues that do not fall into the “largest venue” category. In these cases – which represent approximately 95% of commercial real estate throughout the world – stakeholders need to consider Neutral Host Models that will help to spread the cost of comprehensive in-building networks among a number of investors that stand to benefit.

Technology providers must step-up to make investments count: If a material investment hurdle into next-generation in-building wireless networks is a fear on the part of building owners and/or tenants to invest in technology that can be rendered obsolete before the investments can be adequately depreciated, then technology providers need to work with investment stakeholders to ensure that investments made today remain relevant as the market moves towards 5G. In many cases, this means providing technology with logical and flexible evolution paths from the current state of the art to future developments (i.e. 4G/LTE to 5G). However, beyond this, it can mean working with building owners to help schedule investments in a way that creates attractive ROI models for both the short and long-term.

PIM is described as a form of signal interference that can be caused by either metal components near Passives or two or more carriers sharing the same downlink path in a wireless network, which is becoming more common as wireless networks have become more complex with multiple technology generations such as 2G 3G, LTE and now we will be moving towards 5G. The signals combine to generate unwanted interference, which impacts the signal.
A lot of importance has been given to mitigate PIM nowadays, the reason being the increase in data usage especially indoors, has pushed operators to increase the spectrum for LTE Deployments, which calls for additional frequency bands combined into Indoor DAS by each operator. To stay competitive Telecom operators care a lot about user experience, and PIM is a big hurdle in providing the great user experience. The unwanted signals produced can degrade call quality and reduce the capacity of a wireless system.
High PIM means bad cellular connection and limited bandwidth to the end user, which in turn means lost customers for the operator. Low PIM means strong signals with more bandwidth for more users, which means happy customers and higher revenues for the operator. From a hardware perspective, it means that each and every connection must be designed to minimize PIM and tested to ensure it is installed properly.
Reports show that a slight increase in PIM value could have drastic impacts on downloading speeds. At this point, we should also consider what PIM value is usually acceptable. Well, the answer to that is it depends on which passive products are we talking about. For instance, the products that are close to the base station or the first passive component right after base station (POI, Splitter, and Coupler); -160dBC PIM rating is recommended because of the high power generation of the base station. On the other hand, the passive components that are far away from the base station -150dBC PIM rating would do the job too. By the time the signal reaches the antenna, the RF power is much lower, typically on the order of 100mW (20 dBm). Given the low power level and the high loss between the antenna and the signal source, it’s hard to believe that PIM generated at or beyond the antenna could possibly be high enough to impact system performance. Experience shows that due to the highly non-linear objects often found near antennas, harmful PIM is still possible. This is especially true at low frequencies (700 MHz, 800 MHz and 900 MHz) where the probability of PIM sources occurring inside the antenna’s near field increases. For this reason, PIM is still a concern at or beyond antennas in a DAS.
Regardless of the DAS architecture (Active or Passive DAS), there will be sections where PIM can occur. In a purely Passive DAS, everything beyond the operator’s radio is a place where harmful PIM can occur. With the many splitters, combiners, coaxial cables, and antennas required to distribute the RF signals, the possibility of PIM is in a large number of places. In the image shown below, there are over 150 locations where PIM could occur:
• 64 RF connections
• 31 cable assemblies
• 15 antennas
• 14 power dividers
• 1 hybrid combiner
• 1 RF termination

Linearity in Distributed Antenna System can be improved by using components that are factory tested for PIM, making sure all RF connectors are tight and clean, apply correct assembly torque, and locating antennas away from PIM sources such as pipes, lighting fixtures, and fans.

In today’s competitive world Uninterrupted Power Supply is crucial for businesses; to keep their daily operations running smooth, no matter how big or small the organization is the continuous distribution of power throughout the infrastructure is extremely important to save the costs linked with downtime. UPS power backup is traditionally deployed in two ways; one is a centralised system and the other being distributed system. While they serve the same purpose which is to keep your business (equipment) running through blackouts, electricity fluctuations & other power issues, but they do the job in different ways.

Centralized vs Distributed UPS System:
Both of the ways have their own advantages and disadvantages keeping in mind the ease of installation, reliability, cost & scalability.

1. Ease of installation:
In terms of installation, you might think that a centralized UPS would be easy to install than various distributed UPS systems. Well, the answer is NO, the reason being if the Centralized UPS is a 3-Phase system, it requires extended expertise in installing it properly and regular maintenance. This might not be the case in adopting the distributed approach. You may use a single phase UPS which is far easier to install and requires little or no maintenance at all.

2. Reliability:
The level of critical load the system is supporting is also an important consideration. Popular belief is that a 3 phase UPS is more reliable than a single phase UPS reason being a longer mean time between failure (MTBF) because it has a built-in redundancy feature. Yet it’s not that simple, at times when you have a problem (Technical fault) with a centralized UPS, it will put all of the loads it is protecting at risk. On the other hand, the distributed approach will only affect the chunk of load it is protecting and the UPS can be easily replaced without agitating the entire operation.

3. Cost:
While the initial cost of purchasing a centralized UPS may be less over distributed UPS system, but as mentioned before the complex installation of a centralised UPS will cost much more than a distributed system in general.

4. Scalability:
Keeping in mind changing business needs, at some point in future your power requirements may increase. Adding power backup in a distributed UPS system is easier by simply adding a UPS, whereas in centralized UPS system scalability can be limited and more costly as all of the components are confined to one location.

Depending upon the preferences that are important to your organizational needs; be it cost, efficiency, reliability or ease of use and scalability, the decision rests in the hand of technical managers to determine which strategy is best to opt for.

The fibre optic cable market is growing rapidly, due to the increasing demand for fibre internet. Fibre optic cables transmit data more quickly, more reliably and over greater distances than copper-based cables. Fibre optic cables are made up of several hundred fine fibres, comprising a synthetic silica core infused with boron and germanium and a silica cladding with a lower refractive index. The purpose of the cladding layer is to maintain the optical signal within the core and to add some mechanical strength. Data is transmitted through fibres by shining light through the cable. The light travels as a guided mode, which can be considered for simplicity as bouncing off the walls of the core, known as total internal reflection. The data is transmitted in binary, with a flash of light representing a 1 and an equal period of darkness representing a 0. This allows the data to be transmitted at a rate of more than 120,000 miles per
second!

The installation phase of a fibre optic cable is the most important step towards reliable data transmission at high speed, care must be taken to ensure that the cable while installing is not bent stretched or deformed. If mishandling is done, the best case is that the fibre core will break and be faulty, however, the worst case is that the fibre optic core will be damaged and cause signal distortion, which results in intermittent faults.

The glass core in a fibre optic cable is very fragile, it is found to be slightly thicker than a human hair but made of glass. Single mode fibre uses a special type of glass that is extruded into a solid medium to protect it. Multimode fibre is made from glass but being thicker (at 50 µm compared to 9 µm), is more robust. Because of this, Single mode fibre is more sensitive to breakage than Multimode. The cladding and buffer around the cable core helps to prevent damage; however, if the core is stretched or bent beyond its limit, the core will break.

When the fibre optic is physically compromised, there are two outcomes. One case is that the two glass core pieces are not physically aligned and no laser light will propagate. This case is seen as the best scenario as the fault can be located and fixed. The second case is that the glass core will be partially aligned after the breakage and pass a partial signal. The network may or may not work due to the drop in laser power. Another strong possibility is that the glass core could be damaged instead of being broken. For single mode fibre, the glass core might only crack and cause imperfection in the medium, which would reduce signal propagation and cause reflection. Multimode fibre is more likely to be damaged by flexing and cause loss of power.

Over the past several years’ demand for higher bandwidth and faster speed connections has increased the growth of fibre optic cable market, especially the single mode fibre (SMF) and multimode fibre (MMF). Although these two types of fibre optic cables are used in numerous applications, they are very different from one another in terms of construction, fibre distance, cost and fibre colour. Single mode fibre means the fibre permits one form of light mode to be propagated at a time, however multimode fibre means the fibre can propagate multiple modes at a time. The difference between the two mainly lies in the fibre core diameter, wavelength, light source and bandwidth.

Core Diameter
The core diameter of single mode fibre is way much smaller than the multimode fibre. The typical core diameter for single mode fibre is 9µm and the typical core diameter for multimode fibre is 50µm and 62.5µm. This difference of core diameter enables MMF to have higher “light gathering” ability and simplify connections.

Wavelength & Light Source
The single mode fibre uses a laser or laser diode source to produce the light injected into the cable, the most commonly used single mode fibre wavelength is 1310nm & 1550nm. While due to the large core size of the multimode fibre, light sources like LEDs (light emitting diodes) and VCSELs (vertical cavity surface-emitting lasers) that work at the 850nm and 1310nm wavelength are used in MMF.

Bandwidth
The single mode fibre bandwidth is theoretically unlimited due to the fact that it allows one light of mode to pass through at a time. However, the multimode fibre bandwidth is limited due to its light mode and the maximum bandwidth.

Differences in Distance

According to the chart illustrated above, it can be observed that SMF distance is visibly longer than that of MMF cables at the data rate from 1G to 10G, however, OM3/OM4/OM5 fibre optic supports higher data rate due to the larger core size and also because it supports multiple light modes. The limitation of distance is due to model dispersion, which is a common phenomenon in multimode step-index fibre.
In the end, it can be concluded that both single-mode and multimode have their own characteristics. Single-mode fibre cabling system is suitable for long-reach data transmission applications and widely deployed in carrier networks, MANs and PONs. On the other side, the multimode fibre cabling system has a shorter reach and is widely deployed in the enterprise, data centres, and LANs. No matter which one you choose, choosing the one that best suits your network demands is an important task for every network designer.