Whats the difference between wireless routers with modem and without modem?

S

shankar.c.lal

New Member
Joined
Oct 9, 2014
Messages
1
Reaction score
0
Im really confused pls help.

And can i use a dlink dir 600m as both a modem and a wireless router?
 
Ones without a modem can't connect to your phone line.
 
That is not a modem, it will only be able to extend your wireless coverage.
 
telephone line -----------> modem -------------> router -----------------> computer

But we can get a modem / router combined to make

telephone line -----------> modem / router -----------------> computer

;)
 
The terms are used very sloppily these days, which I find mildly irritating. It's also confusing to newbies, which is probably why you're asking.

A modem is a devices that encodes and decodes a digital signal into analogue form. The word is a contraction of MOdulator-DEModulator. It enables digital information to be transmitted over analogue networks such as the old phone system, or in some fibre optics. A modem at one end encodes the digital signal into analogue form (such as sound) - called modulation - and another modem at the other end decodes the analogue signal back into digital form - called demodulation.

A network switch or switching hub is a device to connect together different computing devices on a computer network. It passes information between the connected devices by using packet switching. The physical connection can be accomplished by cable (such as your typical 4-pair LAN cable with RJ45 plug), or wirelessly (Wi-Fi).

A router is a device that interconnects different networks, by routing data from one network to another through packet switching. The two networks now form one larger network called the internetwork. The Internet is a widely used global internetwork, though not the only one by any means.

It is quite possible and common to combine these various capabilities into one box, though it is extremely rare to find a modem included.

Because ADSL is digital it does not use a modem. Digital data is routed without modulating and demodulating it.

In the pre-ADSL days the most common way of connecting to the internet was via the PSTN (telephone network) using a modem, such as a 56kb/s Hayes. Your computer data travelled in the phone line as sound, just like a normal voice call. A modem at the other end decoded the sounds and converted them back to digital data.

When all-digital ADSL came along, some people erroneously called the box that connected their PC to the phone line (which ADSL also uses) a modem. But it is not a modem. It neither modulates nor demodulates. It is a router.

So widespread has this error become that many manufacturers have followed suit and call their DSL routers modems rather than lose out on sales to the consumer. This of course only compounds the error, and so a whole new generation arises wrongly calling routers modems. Not long from now, some Smart Alec geek will write an article on how stupid his ancestors were to call these things modems, because they clearly are not.

By the way, a network switch for Wi-Fi is these days called a wireless access point (AP). It enables wireless devices to connect to the wired network.

Many common consumer devices (such as the D-Link DSL-2750U) have several of these functions in one box. The router part connects you to the internet via DSL. The network switch part allows you to connect other devices using LAN cables. And the AP part enables wireless connections via Wi-Fi.

Here endeth the lesson

----fin---


(All this laboriously typed out on my phone. It's now time to get up, shower, and get to work.)
 
Last edited:
sajunky said:
In the same way we cannot call 3G modem a 'modem'. Correct, or I missed something, or Wikipedia is wrong? ;)
http://en.wikipedia.org/wiki/Modem#Broadband
Click to expand...
Thanks for that. I clearly need to research ADSL a bit more. I simply assumed it's a purely digital transmission that is not encoded into analogue, though of course all electronic propogations are in wave form. I might well be wrong about ADSL. Always good to discover something new. A nice spur to get into the details of how precisely the data are encoded.
 
Last edited:
It turns out I am wrong about ADSL line transfers being purely digital (as stated in my post above).

The fact is that an ADSL router actually does modulate the digital computer signal and convert it into analogue sound in order to push it down the copper line. It is therefore a true modem. I have been labouring under a misconception for many years, taking the D in DSL to mean the system is entirely digital. It is not.

My apologies for the inaccuracy. I am delighted to have learned something new. :)
 
Last edited:
No problem. :) There was another assumption many times ago that digital signal could only be presented by two voltage levels 0 and 1. If we pass such signal directly to the modulator, we would say "this is a digital modem" - right?

What was true in the case of RS232 serial communication is not true in modern equipment. By example transmission over Ethernet wire is coded in multiple voltage levels. In result Fast Ethernet (100Mb/s) by example is clocked not 100MHz, but around 30MHz. I don't recall exact number, is not an issue. Point is that if we use more quantisation levels, separation between digital and analog signal becomes blured.

What is more important that if we analize signal coming to/from modulator, we will find that there is absolutely not possible to recognise whether it is analog transmission or digital. It looks like a white noise (analog). Interesting fact that any modern transmission system these days is digital, but transmitted signal doesn't look digital anymore :)
Arthur said:
The fact is that an ADSL router actually does modulate the digital computer signal and convert it into analogue sound in order to push it down the copper line. It is therefore a true modem. I have been labouring under a misconception for many years, taking the D in DSL to mean the system is entirely digital. It is not.

My apologies for the inaccuracy. I am delighted to have learned something new. :)
Click to expand...
 
Last edited:
Oh wow... such talking


ADSL router - connects your network to ADSL
WIFI router adds wifi to your network.

Im sure from that you can deduct what an ADSL wifi router does.
 
Arthur said:
It turns out I am wrong about ADSL line transfers being purely digital (as stated in my post above).

The fact is that an ADSL router actually does modulate the digital computer signal and convert it into analogue sound in order to push it down the copper line. It is therefore a true modem. I have been labouring under a misconception for many years, taking the D in DSL to mean the system is entirely digital. It is not.

My apologies for the inaccuracy. I am delighted to have learned something new. :)
Click to expand...

I also believed this for a long time, ISDN is digital though. Thats why ISDN modems were called terminators or something like that. Can't flipping remember now


Also you said a router joins two networks... thats a bridge. A router is an intelligent hub (switch) that can do its own routing... assign IP's and provide DNS.
 
Nerfherder said:
Also you said a router joins two networks... thats a bridge. A router is an intelligent hub (switch) that can do its own routing... assign IP's and provide DNS.
Click to expand...
Hehe. I was trying to simplify for the benefit of the OP, and any simplification loses accuracy at a point. But I clearly had to correct a factual error about DSL.

Still, it seems the terminology has changed over the years as technology has evolved. The first routers were called gateways, which is something else today. On Routers, Wikipedia_Router:

Wikipedia said:
A router is a networking device, commonly specialized hardware, that forwards data packets between computer networks. This creates an overlay internetwork, as a router is connected to two or more data lines from different networks.
Click to expand...
.

And here's their take on Bridges and Bridging:
Wikipedia_Bridging said:
Network bridging is the action taken by network equipment to create an aggregate network from either two or more communication networks, or two or more network segments.[1] Bridging is distinct from routing which allows the networks to communicate independently as separate networks.[2]

A network bridge is a network device that connects multiple network segments.
Click to expand...
 
Last edited:
Arthur said:
Still, it seems the terminology has changed over the years as technology has evolved. The first routers were called gateways, which is something else today. On Routers, Wikipedia_Router:
Click to expand...
Yes, old age routers were frequently called gateways. In fact gateways were very common in the past to join dissimilar networks. Today when all world has standarised on TCP/IP, we don't hear about gateways so frequent. However definition and pupose is the same:
- Routers join similar networks (at least the same lower layer protocols including transport layer).
- Gateways join dissimilar networks. Examples: PC LAN to IBM 3270 mainframe, Windows NT to NetWare, etc...

Gateways can also be used to join similar networks (eq. TCP/IP to TCP/IP) in order to reduce traffic. They use packet routing on higher network layer than TCP.
 
Last edited:
sajunky said:
No problem. :) There was another assumption many times ago that digital signal could only be presented by two voltage levels 0 and 1. If we pass such signal directly to the modulator, we would say "this is a digital modem" - right?

What was true in the case of RS232 serial communication is not true in modern equipment. By example transmission over Ethernet wire is coded in multiple voltage levels. In result Fast Ethernet (100Mb/s) by example is clocked not 100MHz, but around 30MHz. I don't recall exact number, is not an issue. Point is that if we use more quantisation levels, separation between digital and analog signal becomes blured.

What is more important that if we analize signal coming to/from modulator, we will find that there is absolutely not possible to recognise whether it is analog transmission or digital. It looks like a white noise (analog). Interesting fact that any modern transmission system these days is digital, but transmitted signal doesn't look digital anymore :)
Click to expand...

For digital comms it is actually a lot more confusing than this - most long distance comms do not use levels simply because of attenutation of distance affecting those levels. Rather they use states normally in the frequency/phase domain. For example your DSL modem uses a QAM signal which is two waveforms out of phase. In a simple quadrature system the signals would be = in pahse = 00, 90 degrees out of phase = 01, 180 degrees our of phase = 10 270 degrees out of phase = 11 This was we transmit a "symbol" which contains 2 bits of information.
By combining the phase difference and amplitude you can expand this to much bigger symbols - it is however regarded as a pure digital modulation scheme since the demodulation is always quantized to one of a possible number of solutions.

I don't think you can say that because a system is not 1 or 0 it now is no longer digital and sits somewhere between digital and analogue - as long as these is quantized values then it is a digital system. Even flash these days is no longer 1 or 0 but multiple levels.
 
atunguyd said:
For digital comms it is actually a lot more confusing than this - most long distance comms do not use levels simply because of attenutation of distance affecting those levels. Rather they use states normally in the frequency/phase domain. For example your DSL modem uses a QAM signal....
Click to expand...
It is complicated even more when we talk about various modulation techniques.

I just focused on signal properties coming to the modulator or coming out from demodulator.
 
Should make it easy for a first time user guys, from general user's perspective....

1. Wifi router + ADSL modem in one - you just need this one device for Wifi at home, hooked up to ADSL (with phone line jack)
2. Wifi router only - can enable whatever internet connection you have now (that has with an ethernet port, PC, adsl modem, another wifi router, a switch/hub etc etc)
3. Wifi router + 3G - can insert a sim and share 3G via wireless (sim slot or USB port for 3G/4G card)
4. Wifi router + FTTH - connect fibre to the router directly (fibre connector)
 
Hehe, atunguyd. This is indeed very interesting stuff. It's more than a few years since I delved into the physics of these things, which was a personal and professional passion. At a fundamental level, of course, any electronic propagation is analogue at least in the basic waveform. How we freight it with data and then read the bits on the other end is the fascinating part.

Pity the poor OP, who wanted basic classification of common terminology. Your post is a welcome reminder that oversimplification at Levels 2 (Data Link) and 4 (Transport) inevitably result in errors at the Application level. ;)
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X