ADSL and Cable Modems seem to be cost-effective methods for delivering broadband network services. The fundamental difference between ADSL modem and Cable modem is that ADSL modem uses twisted pair cables for providing both voice and data types of services. On the other hand, cable modems work on coaxial cable.
Furthermore, the theoretical carrying capacity of the coaxial cable is hundreds of time higher than the twisted pair cable.
Content: ADSL Modem Vs Cable Modem
|Basis for comparison||ADSL Modem||Cable Modem|
|Type of fibre used||Twisted pair cable||Coaxial cable|
|Maximum offered speed||200 Mbps||1.2 Gbps|
|Security||Dedicated connection provides security.||Insecure|
|Additional options||User can choose ISP||There are no such options.|
|Frequency range||25 KHz - 1.1 MHz||54 - 1000 MHz|
Definition of ADSL Modem
An Asymmetric Digital Subscriber line (ADSL) employs the current copper infrastructure to provide broadband services over POTS. It requires two modems, one at the source, i.e., public carrier’s central office and one at subscribers end. It transmits telephone and internet services in the same twisted pair cable.
ADSL is asymmetric means that it provides different downstream and upstream speeds where downstream speed significantly higher than the upstream speed. The downstream bandwidth is increased through using this uneven partition of the bandwidth which removes the crosstalk between downstream channels of the same amplitude.
Upstream signals suffer more interference because of smaller amplitude and signals are originating from the different distances. The speed could be affected by the distance between the user and public carrier central office, which means signal’s quality degrades the farther it travels.
The major advantage of ADSL is that its bandwidth is not shared among the users. ADSL can cover the distance up to 18000 feet. ADSL modem delivers a frequency range of 25 kHz -1.1 MHz. It provides maximum downlink speed up to 200 Mbps.
Definition of Cable Modem
The Cable modem operates on HFC (Hybrid Fibre Coax) and cable tv coax networks and uses coaxial cable. The major demerit of the strategy that it share the bandwidth between the users, which increases overloading. Cable modem should be capable of filtering out the different traffics such as local LAN broadcasts, DHCP traffic, and ARP packets etc.
Tree or branch type of topology is used in the cable network. In this strategy, if the sender and receiver are on the same branch of network the broadcasted upstream traffic would be received by all the connected host, due to this reason the strategy is very insecure. Cable modem (IEEE 802.14) offers isochronous access and instant access. To resolve collision it employs FIFO first transmission rule, priority and the n-ary tree retransmission rule.
Unlike ADSL network the distance between the user and ISP does not affect the transmission rate of signals. Cable modem delivers frequency range between 54-1000 MHz. It can provide maximum downlink speed up to 1.2 Gbps, depending on the manufacturer and company.
Key Differences Between ADSL and Cable Modem
- ADSL modem uses twisted pair cable while Cable modem uses coaxial cable.
- ADSL can provide speed up to 200 Mbps. On the other hand, Cable modem can provide speed up to 1.2 Gbps.
- The cable modem is insecure as the broadcasted signal is received at all the hosts present the particular branch. In contrast, ADSL modem offers security as each user has a dedicated connection.
- The telephone system is generally more reliable than cable because in case of outage the telephone system has backup power and it continues to work. On the contrary, any power failure in cable system can halt the system instantly.
- The delivered frequency range in ADSL modem is 25 KHz to 1.1 MHz whereas Cable modem delivers frequency range between 54 to 1000 MHz.
Cable modem offers high-speed services as compared to ADSL modem, but ADSL modem provides a security mechanism to the user which cable modem does not provide. In case of the cable modem, bandwidth is shared among the users which degrade transmission speed when a large number of users are accessing services simultaneously.