How to justify text in table columns?

Question

What is the problem with this table?

\newlength\origheight
\setlength\origheight{\textheight}

\begin{landscape}

\begin{table}
    \scalebox{0.5}{
    \begin{tabularx}{\origheight}{@{} >{\bfseries}l *{7}{L} @{}} 

        \toprule
        Protocol name & \textbf{QT} & \textbf{OQTT} & \textbf{STT} 
        & \textbf{BS} & \textbf{CT} & \textbf{QwT} & \textbf{CwT} \\ 
        \midrule

        Protocol feature
        & They use random multi-access way to identify tags. In case of collision, the tags will be asked to send data later with a random time relay.
        & They identify the total number of tags in the interrogation zone. The reader controls every step of the protocol, using commands or queries to split colliding tags into subsets, and further repeatedly split those subsets until identifies all the tags.
        & They are mixture of Aloha and Tree-based protocols. They use two methods. The first is using randomized divisions in Tree-based algorithms, and another is using tree strategies after a collision in Aloha algorithms.
        & It involves transmitting a serial number from the reader to all the tags. Only tags which have equal or lower ID value than the received serial number will respond on request.
        & It is an improvement of QT which uses Bit tracking technology in order to find which bits collided and also where they are.
        & It applies a dynamic bit window to QT. All the tags compare their ID value with the query received and transmit a certain bit amount managed by the reader.
        & It applies the dynamic bit window to CT and adopts two techniques: bit tracking and the bit window.
        \\ \addlinespace
        Disadvantages
        & The reader sends a query and tags, whose ID prefix match that query, respond their full ID.
        & Very complex protocol, uses three technologies. The preprocessing increases the energy consumption of the protocol, especially in dense tag environments.
        & On every collision, the full tag response, apart from the initial query bits, is wasted.
        & The reader restart the reading process after a tag is identified.
        & It wastes a high number of tag bits on every collision, which increases the energy consumed by the reader during the process.
        & When the calculated ws is high, the reader command needs a high number of bits to represent it. That leads to a wastage of the reader bits.
        & Increase the number of reader bits
        \\ \addlinespace
        RTF/TTF 
        & RTF & RTF & RTF & RTF & RTF & RTF & RTF 
        \\
        Efficiency
        & 34.6\% & 61.4\% & 58\% & & 35\% & 80\% & 61\% 
        \\
        System cost 
        & Very low & Very expensive & Expensive & Medium & Low & Medium & Medium
        \\
        Complexity 
        & Very simple & Very high & High & Medium & Simple & Medium & Medium 
        \\
        \bottomrule 
    \end{tabularx}
}
    \caption{A comparison of tree-based protocols}
    \label{tab:ComparationThree}
\end{table}
\end{landscape}

Look how looks now. I want to be more wide to fit on whole page

Answer 1

(This version of answer addresses the heavily modified form of the OP's query and code, which is based the original form of my answer.)

The code in your revised query contains the instruction

\begin{tabularx}{\textwidth}{@{} >{\bfseries}l *{5}{X} @{}}

Since your table now contains 7 data columns, not 5 as before, you need to change this instruction to

\begin{tabularx}{\textwidth}{@{} >{\bfseries}l *{7}{X} @{}}

The X column type performs full justification. Given that the 7 data columns are quite narrow, full justification is bound to create large and unsightly inter-word gaps. In my view, it's preferable to typeset the material ragged-right. This may be done by adding the instructions

\usepackage{ragged2e}
\newcolumntype{L}{>{\RaggedRight\arraybackslash}X}

to the preamble and later on writing

\begin{tabularx}{\textwidth}{@{} >{\bfseries}l *{7}{L} @{}}

However, if you don't like the resulting look, simply revert to

\begin{tabularx}{\textwidth}{@{} >{\bfseries}l *{7}{X} @{}}

A separate point: Following up on your comments, I made the change from a sidewaystable setup to a combined landscape/table setup. That way, the table is rotated in the pdf file itself, removing any need for readers to crane their necks.

\documentclass{article}
\usepackage[a4paper,margin=2.5cm]{geometry} 
\usepackage{pdflscape,booktabs,tabularx,ragged2e}
\newcolumntype{L}{>{\RaggedRight\arraybackslash}X} % raggedright rather than full justification
\begin{document}

%% save the original value of the \textheight parameter:
\newlength\origheight
\setlength\origheight{\textheight}

\begin{landscape}
\begin{table}
\begin{tabularx}{\origheight}{@{} >{\bfseries}l *{7}{L} @{}} 

\toprule
Protocol name & \textbf{QT} & \textbf{OQTT} & \textbf{STT} 
& \textbf{BS} & \textbf{CT} & \textbf{QwT} & \textbf{CwT} \\ 
\midrule

Protocol feature
& They use random multi-access way to identify tags. In case of collision, the tags will be asked to send data later with a random time relay.
& They identify the total number of tags in the interrogation zone. The reader controls every step of the protocol, using commands or queries to split colliding tags into subsets, and further repeatedly split those subsets until identifies all the tags.
& They are mixture of Aloha and Tree-based protocols. They use two methods. The first is using randomized divisions in Tree-based algorithms, and another is using tree strategies after a collision in Aloha algorithms.
& It involves transmitting a serial number from the reader to all the tags. Only tags which have equal or lower ID value than the received serial number will respond on request.
& It is an improvement of QT which uses Bit tracking technology in order to find which bits collided and also where they are.
& It applies a dynamic bit window to QT. All the tags compare their ID value with the query received and transmit a certain bit amount managed by the reader.
& It applies the dynamic bit window to CT and adopts two techniques: bit tracking and the bit window.
\\ \addlinespace
Disadvantages
& The reader sends a query and tags, whose ID prefix match that query, respond their full ID.
& Very complex protocol, uses three technologies. The preprocessing increases the energy consumption of the protocol, especially in dense tag environments.
& On every collision, the full tag response, apart from the initial query bits, is wasted.
& The reader restart the reading process after a tag is identified.
& It wastes a high number of tag bits on every collision, which increases the energy consumed by the reader during the process.
& When the calculated ws is high, the reader command needs a high number of bits to represent it. That leads to a wastage of the reader bits.
& Increase the number of reader bits
\\ \addlinespace
RTF/TTF 
& RTF & RTF & RTF & RTF & RTF & RTF & RTF 
\\
Efficiency
& 34.6\% & 61.4\% & 58\% & & 35\% & 80\% & 61\% 
\\
System cost 
& Very low & Very expensive & Expensive & Medium & Low & Medium & Medium
\\
Complexity 
& Very simple & Very high & High & Medium & Simple & Medium & Medium 
\\
\bottomrule 
\end{tabularx}
\caption{A comparison of tree-based protocols}
\label{tab:ComparationThree}
\end{table}
\end{landscape}
\end{document}