What is SDSL? We Look at 4 Comparisons Between SDSL vs ADSL
SDSL (Symmetric Digital Subscriber Line) is a type of broadband connection that offers equal upload and download speeds, ideal for businesses requiring reliable data transfer in both directions.
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What is the Difference Between SDSL & ADSL?
Feature
SDSL
ADSL
Price
More expensive
Less expensive
Download Speeds
High speed
High speed
Ideal for
Businesses who require high uploads and downloads
Businesses/residentials with high download needs
Upload Speeds
Same as download speed
Quite a bit slower than download speed
How Does SDSL Work?
SDSL is a pair of wires called the ‘local loop’, used to transmit data digitally; initially, these wires were used for audio transmission, but using frequencies above allows for data transmission instead. Two circuits are integrated, one for upstream transmission and the other for downstream transmission, reducing the likelihood of collisions and delays.
Here’s how SDSL works:
Symmetric Speeds: Unlike asymmetric DSL (ADSL), which provides faster download speeds than upload speeds, SDSL offers symmetric speeds, meaning the upload and download speeds are the same. This makes SDSL suitable for applications that require high-speed data transfer in both directions, such as video conferencing, file sharing, and online backups.
Frequency : SDSL divides the frequency spectrum of the copper telephone line into separate channels for upstream (upload) and downstream (download) data transmission.
Modulation : SDSL uses modulation techniques, such as Discrete Multitone Modulation (DMT) or Carrierless Amplitude and Phase Modulation (CAP), to encode digital data into analogue signals that can be transmitted over copper wires.
Line Conditioning : SDSL requires line conditioning to optimise the performance and reliability of the copper telephone lines. Line conditioning involves noise filtering, signal equalisation, and error correction to minimise signal degradation and maintain stable connectivity over long distances.
DSL access multiplexers: At the service provider’s central office (CO), DSL access multiplexers (DSLAMs) are installed to manage and terminate the SDSL connections from multiple customer premises.
Router : At the customer premises, SDSL requires a compatible modem or router to establish and maintain the service provider’s network connection.
Activation : To activate SDSL service, the service provider configures the customer’s line at the central office and provisions the necessary settings on the customer premises equipment, and once this is activated, customers can connect their devices to the SDSL modem/router and access high-speed internet connectivity with symmetric upload and download speeds.
Below is a table explaining the difference between different lines
Type
Download
Speed
Upload
Speed
Distance
from CO
ADSL
1.5 to 9 Mbps
16-640 Kbps
18,000 feet
SDSL
1.544 Mbps
1.544 Mbps
10,000 feet
HDSL
1.544 Mbps
1.544 Mbps
10,000 feet
VDSL
20-50+ Mbps
Up to 20 Mbps
<5,000 feet
SDSL Benefits
SDSLs are optimal for businesses prioritising uploading speeds to allow faster backup and more satisfied customers. Whilst they cannot allow simultaneous phone usage, they can maximise the full potential of their internet connection and are less costly than fibre optics, proving useful for smaller companies. Some benefits of SDSL include the following:
They can significantly improve the quality of VoIP calls
Provides equal speeds for data uploads and downloads
Connection speeds that are typically much faster than ADSL
Ultimately save your business time and money
Overall, the type of network needed for a business depends on why they use the internet and what type of services they provide. Therefore, for a company to choose an SDSL, they should deliberate on what upload and download speeds they require and whether they could manage without a simultaneous phone and internet connection.
SDSL Providers
SDSL providers UK
Even though SDSL is the preferred network for many businesses, this does not mean many providers offer it. There are a limited number of companies in the UK that can provide SDSL, but they do exist. Unfortunately, prices vary and are not cheap. Let’s explore a few UK based SDSL providers below:
Spitfire: A London-based company that has been around since 1988, with gross revenue of over £26 million. Their most popular package for SDSL includes 2Mbps upload and download speeds for £69 a month. This includes a free router and peak time priority with a two-year contract, explicitly targeted at low-value latency businesses and reduced packet loss. Their most popular package for SDSL includes 2Mbps upload and download speeds for £69 a month. This includes a free router and peak time priority with a two-year contract, explicitly targeted at low-value latency businesses and reduced packet loss. There are fewer delays and more successful and instant internet connections.
Hotchilli : A more expensive provider of SDSL is Hotchilli, with the same 2Mbps speeds costing over £300 monthly, not including installation time. Due to the exclusivity of this network, costs are higher.
BT Business : BT Business offers SDSL services tailored to the needs of businesses, providing symmetric upload and download speeds for reliable data transmission.
TalkTalk Business : TalkTalk Business offers SDSL solutions designed for businesses of all sizes, providing symmetric connectivity with guaranteed bandwidth for critical applications.
Zen Internet : Zen Internet offers SDSL services with symmetric speeds and dedicated bandwidth, ideal for businesses requiring high-performance internet connectivity.
Daisy Communications : Daisy Communications provides SDSL connectivity solutions for businesses, offering symmetric speeds and reliable performance for mission-critical applications.
XLN Telecom : XLN Telecom offers SDSL services aimed at small and medium-sized businesses, providing symmetric upload and download speeds to support business operations.
Gradwell Communications : Gradwell Communications offers SDSL solutions tailored to the requirements of businesses, delivering symmetric connectivity for enhanced reliability and performance.
SDSL Costs
A Handy Youtube Guide About SDSL
VIDEO
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SDSL FAQS
What is the difference between SDSL and ADSL
Upload and download speeds: Essentially, a Symmetric Digital Subscriber Line and Asymmetric Digital Subscriber Line (ADSL) are opposite types of DSL. ADSL upstream and downstream data transmissions have different bandwidths, so one has a faster speed than the other. This reflects that SDSL is more suited to businesses as they need equal speeds to upload and download data. ASDL may be more tailored towards homeowners that require rapid download speeds to surf the web and download files but do not necessarily upload as much information to the web as there is often no need, hence why downstream is prioritised.
Use of a telephone line: As aforementioned, SDSL installation is relatively straightforward as only internet access is needed. On the other hand, ADSL can utilise a telephone and an internet connection. This is because they use a different frequency to the telephone line, so both can be used simultaneously, thus why the installation process is a little more complex. Instead of the DSL cable connecting straight from the socket to the modem, a phone line splitter connects to the socket and then the DSL cable can be inserted to connect to the modem.
Cost: SDSL and ASDL are also similar, with SDSL being slightly more costly. It is difficult to compare because these DSLs have different speeds, so the evaluation is not fair, but in general, both of these prices are extensively cheaper than fibre. DSL is more available geographically, whereas fibre optics are less accessible and, therefore, more costly due to their rarity; 98% of the UK can access DSL, whilst only around 6% can access fibre. Fibres also reach greater distances and are more reliable, whilst DSLs degenerate the further the target destination is from the modem, providing lower bandwidths and, therefore, slower speeds.
Standardisation: Standardising something makes it the most common and significantly more used than others. SDSL is considered more outdated than other alternatives and so-termed ‘proprietary’, suggesting it is less common and more exclusive, which may be why fewer people use it.
Other useful links about leased lines:
Ethernet First Mile Costs
EFM Business Broadband
Leased Lines – The Best Networks
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